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  • Citing Sources

Citing Sources: What are citations and why should I use them?

What is a citation.

Citations are a way of giving credit when certain material in your work came from another source. It also gives your readers the information necessary to find that source again-- it provides an important roadmap to your research process. Whenever you use sources such as books, journals or websites in your research, you must give credit to the original author by citing the source. 

Why do researchers cite?

Scholarship is a conversation  and scholars use citations not only to  give credit  to original creators and thinkers, but also to  add strength and authority  to their own work.  By citing their sources, scholars are  placing their work in a specific context  to show where they “fit” within the larger conversation.  Citations are also a great way to  leave a trail  intended to help others who may want to explore the conversation or use the sources in their own work.

In short, citations

(1) give credit

(2) add strength and authority to your work

(3) place your work in a specific context

(4) leave a trail for other scholars

"Good citations should reveal your sources, not conceal them. They should honeslty reflect the research you conducted." (Lipson 4)

Lipson, Charles. "Why Cite?"  Cite Right: A Quick Guide to Citation Styles--MLA, APA, Chicago, the Sciences, Professions, and More . Chicago: U of Chicago, 2006. Print.

What does a citation look like?

Different subject disciplines call for citation information to be written in very specific order, capitalization, and punctuation. There are therefore many different style formats. Three popular citation formats are MLA Style (for humanities articles) and APA or Chicago (for social sciences articles).

MLA style (print journal article):  

Whisenant, Warren A. "How Women Have Fared as Interscholastic Athletic Administrators Since the Passage of Title IX." Sex Roles Vol. 49.3 (2003): 179-182.

APA style (print journal article):

Whisenant, W. A. (2003) How Women Have Fared as Interscholastic Athletic Administrators Since the Passage of Title IX. Sex Roles , 49 (3), 179-182.

Chicago style (print journal article):

Whisenant, Warren A. "How Women Have Fared as Interscholastic Athletic Administrators Since the Passage of Title IX." Sex Roles 49, no. 3 (2003): 179-182.

No matter which style you use, all citations require the same basic information:

  • Author or Creator
  • Container (e.g., Journal or magazine, website, edited book)
  • Date of creation or publication
  • Publisher 

You are most likely to have easy access to all of your citation information when you find it in the first place. Take note of this information up front, and it will be much easier to cite it effectively later.

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What Is a Citation?

Definition, Styles, and Examples

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  • M.A., Modern English and American Literature, University of Leicester
  • B.A., English, State University of New York

In any research paper, you draw on the work of other researchers and writers, and you must document their contributions by citing your sources, say Diana Hacker and Nancy Sommers in "A Pocket Style Manual, Eighth Edition." Citations, then, are the means by which you credit other researchers and writers when you use their work in your papers. Understanding how to cite sources can be tricky, particularly since there are different styles for writing papers , including the American Psychological Association, Modern Language Association, and Chicago (Turabian) styles. Electronic sources also come with their own specific citation rules in each of these styles. It's important to learn proper citation styles to avoid  plagiarism  in your research papers.

APA Citations

American Psychological Association (APA) style is often used in social sciences and other disciplines. With APA or any of the styles listed in this paper, you need to use a citation if you quote text from another source, paraphrase an author or authors' ideas, or refer to her work, such as a study, original thinking, or even an elegant turn of phrase. When you cite a source, you can't simply repeat most of the words from the work to which you are referring. You have to put the ideas into your own words, or you need to quote the text directly.

There are two parts to citations for APA and other styles: the short-form in line, which directs readers to a full entry at the end of a chapter or book. An in-line citation differs from a footnote, which is a note placed at the bottom of a page. An in-line citation—also called the  in-text citation —is placed within a line of text. To create an in-line citation, cite the name of the author and the date (in parentheses) of the article, report, book, or study, as this example from "A Pocket Style Manual" shows:

Cubuku (2012) argued that for a student-centered approach to work, students must maintain "ownership for thier goals and activities" (p. 64).

Note how you list the page number at the end of the in-text citation in parentheses followed by a period (if it is at the end of a sentence). If there are two authors, list the last name of each, as in:

"According to Donitsa-Schmidt and Zurzovsky (2014), ..."

If there are more than two authors, list the last name of the first author followed by the words "et al.," as in:

Herman et al. (2012) tracked 42 students over a three-year period (p. 49).

At the end of your paper, attach one or more pages titled "References." That section is essentially your biography. Readers of your paper can then turn to the references listing to read the full citations for each of the works you cited. There are actually many variations for references citations depending, for example, on whether you are citing a book, journal article, or newspaper story, or the many different kinds of media, including audio recordings and film.

the most common citation is to books. For such a citation, list the last name of the author, followed by a comma, followed by the first initial(s) of the author(s), followed by a period. You would put the year the book was published in parentheses followed by a period, then the title of the book in italics using sentence case , followed by a comma, the place of publication, followed by a colon, and then the publisher, followed by a period. "A Pocket Style Manual" gives this example:

Rosenberg, T. (2011). Join the club: How peer pressure can transform the world . New York, NY: Norton.​

Though the citations here won't print this way, use a hanging indent for the second and any subsequent lines in each citation. In a hanging indent in APA style, you indent every line after the first.

MLA Citations

MLA style is often used in English and other humanities papers. MLA follows the author-page style for in-text citations, notes Purdue OWL, an excellent citation, grammar, and writing website operated by Purdue University. Purdue gives this example of an in-text citation, which is also called parenthetical citation in MLA style. Note that in MLA style, page numbers don’t typically appear unless the sentence or passage is a direct quote from the original, as is the case here:

Romantic poetry is characterized by the "spontaneous overflow of powerful feelings" (Wordsworth 263).

At the end of the paper, attach a "Works Cited" page or pages, which is equivalent to the "References" section in APA style. "Works Cited" section citations are very similar in MLA and APA style, as in this example of a work with multiple authors from Purdue OWL:

Warner, Ralph, et al.  How to Buy a House in California . Edited by Alayna Schroeder, 12th ed., Nolo, 2009.

Note that you would also use a hanging indent in MLA, but it tends to be a bit shorter; move the second and subsequent lines in by three spaces. Spell out the first name of the author(s) in MLA style; add a comma before "et al."; use title case for the book, journal, or article title; omit the place of publication information; follow the name of the publisher with a comma; and list the date of publication at the end.

Chicago Style Citations

Chicago is the oldest of the three major writing and citation styles in the United States, having begun with the 1906 publication of the first Chicago style guide. For in-text citations, Chicago style, which comes from the "Chicago Manual of Style" from the University of Chicago Press, is pretty simple: the author's last name, date of publication, a comma, and page numbers, all in parentheses, as follows:

(Murav 2011, 219-220)

At the end of the paper, insert a list of references, which in Chicago style is called a bibliography. Books, journals, and other articles are cited in a manner similar to APA and MLA style. List the author's last name, a comma, and the full first name, followed by the title of the book in italics and title case, the place of publication, followed by a colon, followed by the publisher's name, a comma, and the date of publication, all in parentheses, followed by a comma and the page numbers.

Kate L. Turabian, in "A Manual for Writers" (a student-geared version of Chicago style), gives the following example:

Gladwell, Malcolm,  The Tipping Point: How Little Things Can Make a Big Difference  (Boston: Little Brown, 2000), 64-65.

You also use a hanging indent in the bibliography section of a Chicago style paper, with the indent moved in three spaces. For article or journal titles, list the title in regular (not italic) type encased in quotation marks.

Electronic Sources

Electronic source citations are similar to citations of published works except for two issues: You need to include the URL of the source, and a large percentage of online sources may not list an author. 

In APA style, for example, list an online source in the same way you would cite a book or article, except that you need to include the type of information you are accessing (in parentheses), as well as the URL. If the online source lacks a listed author, start with the name of the group or agency providing the information. "A Pocket Manual of Style" provides the following example of an APA electronic source citation:

U.S. Department of Agriculture, Economic Research Service. (2011). Daily intake of nutrients by food source: 2005-08 . ​[Data set]. Retrieved from http:www.ers.usda.gov/data-products/food-consumption-and-nutrient-intakes.aspx.

As with other citations, use a hanging indent for the second, third, and fourth lines of this source. For Chicago style, use the same method as described previously but add the URL, as in this example:

Brown, David. "New Burden of Disease Study Shows World's People Living Longer but with More Disability," Washington Post , December 12, 2012. http://www.washingtonpost.com/.

Note that Chicago style includes only the home-page URL and not the full URL; that can change, however, from one regime to the next.

MLA style used to require you to list the date you accessed the information, but that's no longer the case. To cite an electronic source, use the same style as discussed previously, but replace the period after the date with a comma and then list the URL.

  • What Is a Bibliography?
  • Bibliography: Definition and Examples
  • MLA Bibliography or Works Cited
  • What Is a Senior Thesis?
  • APA In-Text Citations
  • Turabian Style Guide With Examples
  • How to Write a Bibliography For a Science Fair Project
  • MLA Sample Pages
  • 36 Common Prefixes in English
  • How to Use Parentheses in Writing
  • Title Page Examples and Formats
  • MLA Style Parenthetical Citations
  • Formatting Papers in Chicago Style
  • Formatting APA Headings and Subheadings
  • Tips for Typing an Academic Paper on a Computer
  • Examples of Signal Phrases in Grammar and Composition

Table of Contents

Collaboration, information literacy, writing process, citation – definition – introduction to citation in academic & professional writing.

  • © 2023 by Joseph M. Moxley - University of South Florida

Explore the different ways to cite sources in academic and professional writing, including in-text (Parenthetical), numerical, and note citations.

meaning of research citation

What is a Citation?

A “ citation ” refers to the act of integrating ideas or words from another source into your speech or writing , along with adhering to the specific discourse conventions (or standardized ways of acknowledging sources) in a particular academic or professional field . “Citations” are required in academic and professional writing when writers summarize , paraphrase , or quote the words or ideas others. Writers may also cite known experts to enhance the authority of their arguments and observations.

In both academic and professional settings, the practice of citing sources—whether through quotations , paraphrasing , or summarizing —is a fundamental mark of professionalism. Being capable of citing sources correctly and critiquing the citations of others is a basic literacy in a knowledge economy.

Most generally, “citation” refers to the act of crediting a source of information . While “citation” is the formal term, there are several colloquial synonyms that people might use interchangeably, such as “ attribution ,” “reference,” or “mention.” In more casual or conversational settings, phrases like “backing up” one’s claim or providing “proof” might be used. When writers or speakers incorporate information from an external source, they might say they are “citing,” “ attributing ,” or “referencing” that source.

Related Concepts: Academic Dishonesty ; Archive ; Authority in Academic Writing ; Canon ; Copyright ; Discourse ; Hermeneutics ; Information Has Value ; Intellectual Property ; Paraphrase ; Plagiarism ; Quotation ; Scholarship as a Conversation ; Summary

What Are The Three Major Ways of Citing Sources inside a Text?

While there are many different citation styles, as discussed below, there are only three major types of citations:

  • In-text Citation (aka Parenthetical Citation)
  • Numerical citation
  • Note Citations

In-text Citation (aka Parenthetical Citation )

In-text Citation refers to the practice of placing bibliographical information in parentheses when sources/information are first introduced in a quote , paraphrase , or summary . The in-text citation is typically shorter and directs the reader to the full citation in the bibliography or reference list. In essence, all in-text citations are citations, but not all citations are in-text citations.

APA Example

When using APA style, writers place the author’s name, year, and page number (when available) in parentheses.

  • “As of 2022, about 12,700 nuclear warheads are still estimated to be in use, of which more than 9,400 are in military stockpiles for use by missiles, aircraft, ships and submarines” (Eagle, 2022).

And then at the end of their text, they list all of the sources they cited in the text, providing all of the bibliographical information users need to track down the source and read it:

  • Eagle, J. (2022, March 21). Animated chart: Nuclear warheads by country (1945-2022). Visual Capitalist .

Numerical Citation

Numerical Citation refers to when writers use numbers in brackets or superscript rather than parentheses to indicate to readers when they are quoting , paraphrasing , or summarizing :

IEEE Example

  • “As of 2022, about 12,700 nuclear warheads are still estimated to be in use, of which more than 9,400 are in military stockpiles for use by missiles, aircraft, ships and submarines” [1]

Subsequently, in the reference list at the end of their text, writers provided the bibliographic information following the order of the citations in the text:

Chicago (Turabian) Example

  • [1]J. Eagle, “Animated Chart: Nuclear Warheads by Country (1945-2022),” Visual Capitalist , Mar. 21, 2022. (accessed Jan. 03, 2023).

[ See Inclusive – Inclusive Language for a full-length example of Numerical Citations ]

Note Citation

Note Citations refers to when writers place citations numbers just as they do with numerical citations AND then provide all of the required bibliographical information in the text–as opposed to providing all that information at the end of the text in a list of references:

  • “As of 2022, about 12,700 nuclear warheads are still estimated to be in use, of which more than  9,400  are in military stockpiles for use by missiles, aircraft, ships and submarines” J. Eagle, “Animated Chart: Nuclear Warheads by Country (1945-2022),” Visual Capitalist , Mar. 21, 2022. (accessed Jan. 03, 2023).

meaning of research citation

What Do All Citations Styles Have in Common?

Regardless of which citation style is used, attributions typically provide four types of bibliographical information :

  • Name of Author(s)
  • Title of source, whether it’s a book/article/website, etc
  • Date of publication, if available
  • Publisher information.

What Are the Most Popular Citation Styles?

Professional organizations (communities of practice) have unique ways of formatting citations. (See Wikipedia for a good listing of citation styles .)

Although style guides differ in regard to where the author’s name or publishing source is listed, they are all designed to ensure that proper credit is given to authors. As you know from your experience as a writer, developing insights and conducting original research is difficult and time consuming, so you can understand why people want to receive proper credit for their original ideas.

  • MLA Handbook, 9th Edition Modern Language Association style is primarily used in the fields of English and foreign languages.
  • Publication Manual of the APA: 7th Edition American Psychological Association’s style guide is used in psychology and education. Education and social science professors commonly ask students to follow the APA style for citing and documenting sources. APA differs from MLA in a number of ways, including the overall structure and format of the essay, but the major distinction between the two is APA’s use of the year of publication, rather than the page on which a particular quotation appears, for the in-text citation. APA requires in-text publication dates because of the particular importance of a study’s currency to research reports in the social sciences.
  • Chicago Style is used in many social science fields.
  • CSE (Council of Science Editors) is used by the scientific community
  • IEEE (Institute of Electrical and Electronic Engineers) is used by the engineering community.

What Critical Perspectives Do Readers Use to Assess Your Citations?

Citation in speech and writing serves as a barometer of ethos , especially trustworthiness . When audiences are engaged in critical literacy practices , they are likely to question a source’s

When audiences check the archive and find that authors are making inconsistent quotations , they are likely to question the character or ethos of the author.

In other words, subject matter experts tend to be well versed in the ongoing conversations that characterize the works of other subject matter experts. Experienced researchers tend to engage in strategic searching of the archive . They engage in critical literacy practices , asking questions, such as

  • What is the status of knowledge on the topic ?
  • What is the ebb and flow of research on the topic –over time?
  • What are the canonical texts ?
  • Who are the pioneers? How has their work changed the conversation?
  • What knowledge claims are currently being debated?

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APA - Publication Manual of the APA: 7th Edition

APA - Publication Manual of the APA: 7th Edition

Attribution - What Is The Role of Attribution In Academic & Professional Writing?

Attribution - What Is The Role of Attribution In Academic & Professional Writing?

Citation Guide - Learn How to Cite Sources in Academic and Professional Writing

Citation Guide - Learn How to Cite Sources in Academic and Professional Writing

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MLA - MLA Handbook, 9th Edition

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APA - Publication Manual of the APA: 7th Edition

  • Joseph M. Moxley

Attribution refers to the practice of crediting original sources for information or ideas. It encompasses recognizing authors, understanding their credentials, and correctly citing their work in your own speech and...

Citation Guide - Learn How to Cite Sources in Academic and Professional Writing

Citation isn’t just about adhering to prescribed rules or ensuring each dot and comma is in its rightful place. It’s a rhetorical, fluid, intuitive process where writers must balance the...

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Research Skills Tutorial

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  • Portfolio Activity 1
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  • Credible Sources
  • What Does the Information Source Tell You About Itself?
  • Reliability
  • Some More About Validity
  • Portfolio Activity 5
  • What Is Citing?
  • What Is a Citation?
  • Citation Styles
  • Citing Tools and Tips
  • Practice Activity 6
  • Practice Activity 7 - Final Project

What Is A Citation?

When to cite.

A citation is a reference to the source of information used in your research. Any time you directly quote, paraphrase or summarize the essential elements of someone else's idea in your work, an in-text citation should follow. An in-text citation is a brief notation within the text of your paper or presentation which refers the reader to a fuller notation, or end-of-paper citation , that provides all necessary details about that source of information. Direct quotations should be surrounded by quotations marks and are generally used when the idea you want to capture is best expressed by the source.  Paraphrasing and summarizing involve rewording an essential idea from someone else's work, usually to either condense the point or to make it better fit your writing style. You do not have to cite your own ideas, unless they have been published. And you do not have to cite  common knowledge , or information that most people in your audience would know without having to look it up.

In-Text Citations

In-text citations alert the reader to an idea from an outside source.  

Parenthetical Notes

In MLA and APA styles, in-text citations usually appear as parenthetical notes (sometimes called parenthetical documentation ). They are called parenthetical notes because brief information about the source, usually the author's name, year of publication, and page number, is enclosed in parentheses as follows:  

MLA style: (Smith 263)

APA style: (Smith, 2013, p. 263)  

Parenthetical notes are inserted into the text of the paper at the end of a sentence or paragraph:>

Example of a parenthetical in-text citation.

In MLA and APA styles, in-text citations are associated with end-of-paper citations that provide full details about an information source. Note: Different source types and situations require different information within the parentheses. Refer to a style guide for the style you are using for details.

Note Numbers

In Chicago and CSE styles, in-text citations usually appear as superscript numerals, or note numbers , as follows:

meaning of research citation

These note numbers are associated with full citations that can appear as footnotes (bottom of page), endnotes (end of chapter or paper), or lists of cited references at the end of the paper.  

End-of-Paper Citations

End-of-paper citations, as well as footnotes and endnotes, include  full details about a source of information.  Citations contain different pieces of identifying information about your source depending on what type of source it is. In academic research, your sources will most commonly be articles from scholarly journals, and the citation for an article typically includes:  

  • article title
  • publication information (journal title, date, volume, issue, pages, etc.)
  • DOI (digital object identifier).
  • URL of the information source itself
  • URL of the journal that published the article

There are many other types of sources you might use, including books, book chapters, films, song lyrics, musical scores, interviews, e-mails, blog entries, art works, lectures, websites and more. To determine which details are required for a citation for a particular source type, find that source type within the style guide for the citation style you are using. At the end of your research paper, full citations should be listed in order according to the citation style you are using:

  • In MLA style, this list is called a W orks Cited page.  
  • In APA style, it is called a References page.
  • In CSE style, it is called a C ited References page.
  • And, in Chicago style, there may be both a Notes page and a Bibliography page. 

meaning of research citation

Citations  In Library Databases

When you search the library's databases for articles or e-books, the list of search results you see is actually a list of full citations. Instead of being formatted according to MLA, APA, CSE, or Chicago style, these citations are formatted according to the database vendor's style. It is up to you to take the source information you find in a library database (or elsewhere) and format it according to the citation style you are using.

Database results list containing citation information.

Accessibility Note

Please note: If you need to request accommodations with content linked to on this guide, on the basis of a disability, please contact Accessibility Resources and Services by emailing them .  Requests for accommodations should be submitted as early as possible to allow for sufficient planning. If you have questions, please visit the Accessibility Resources and Services website .

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Citing sources: Overview

  • Citation style guides

Manage your references

Use these tools to help you organize and cite your references:

  • Citation Management and Writing Tools

If you have questions after consulting this guide about how to cite, please contact your advisor/professor or the writing and communication center .

Why citing is important

It's important to cite sources you used in your research for several reasons:

  • To show your reader you've done proper research by listing sources you used to get your information
  • To be a responsible scholar by giving credit to other researchers and acknowledging their ideas
  • To avoid plagiarism by quoting words and ideas used by other authors
  • To allow your reader to track down the sources you used by citing them accurately in your paper by way of footnotes, a bibliography or reference list

About citations

Citing a source means that you show, within the body of your text, that you took words, ideas, figures, images, etc. from another place.

Citations are a short way to uniquely identify a published work (e.g. book, article, chapter, web site).  They are found in bibliographies and reference lists and are also collected in article and book databases.

Citations consist of standard elements, and contain all the information necessary to identify and track down publications, including:

  • author name(s)
  • titles of books, articles, and journals
  • date of publication
  • page numbers
  • volume and issue numbers (for articles)

Citations may look different, depending on what is being cited and which style was used to create them. Choose an appropriate style guide for your needs.  Here is an example of an article citation using four different citation styles.  Notice the common elements as mentioned above:

Author - R. Langer

Article Title - New Methods of Drug Delivery

Source Title - Science

Volume and issue - Vol 249, issue 4976

Publication Date - 1990

Page numbers - 1527-1533

American Chemical Society (ACS) style:

Langer, R. New Methods of Drug Delivery. Science 1990 , 249 , 1527-1533.

IEEE Style:

R. Langer, " New Methods of Drug Delivery," Science , vol. 249 , pp. 1527-1533 , SEP 28, 1990 .

American Psychological Association   (APA) style:

Langer, R. (1990) . New methods of drug delivery. Science , 249 (4976), 1527-1533.

Modern Language Association (MLA) style:

Langer, R. " New Methods of Drug Delivery." Science 249.4976 (1990) : 1527-33.

What to cite

You must cite:

  • Facts, figures, ideas, or other information that is not common knowledge

Publications that must be cited include:  books, book chapters, articles, web pages, theses, etc.

Another person's exact words should be quoted and cited to show proper credit 

When in doubt, be safe and cite your source!

Avoiding plagiarism

Plagiarism occurs when you borrow another's words (or ideas) and do not acknowledge that you have done so. In this culture, we consider our words and ideas intellectual property; like a car or any other possession, we believe our words belong to us and cannot be used without our permission.

Plagiarism is a very serious offense. If it is found that you have plagiarized -- deliberately or inadvertently -- you may face serious consequences. In some instances, plagiarism has meant that students have had to leave the institutions where they were studying.

The best way to avoid plagiarism is to cite your sources - both within the body of your paper and in a bibliography of sources you used at the end of your paper.

Some useful links about plagiarism:

  • MIT Academic Integrity Overview on citing sources and avoiding plagiarism at MIT.
  • Avoiding Plagiarism From the MIT Writing and Communication Center.
  • Plagiarism: What It is and How to Recognize and Avoid It From Indiana University's Writing Tutorial Services.
  • Plagiarism- Overview A resource from Purdue University.
  • Next: Citation style guides >>
  • Last Updated: Jan 16, 2024 7:02 AM
  • URL: https://libguides.mit.edu/citing

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Citation Guide

What is a citation, scholarly versus popular publications, citation components (credo), writing help.

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A citation is the way you tell your readers that certain material in your work came from another source and gives your readers the information necessary to find that source again. Citations may include: Information about the Author(s) or Editor(s).

  • The Title of the work
  • The Publisher
  • The Date published
  • The Page Numbers of the material you are referencing
  • Why should I cite sources?

Giving credit to the original author by citing sources is the only way to use other people's work without plagiarizing. But there are a number of other reasons to cite sources:

  • Citations are extremely helpful to anyone who wants to find out more about your ideas and where they came from.
  • Not all sources are good or right for your project -- your own ideas may often be more accurate or interesting than those of your sources. Proper citation will keep you from taking the rap for someone else's bad ideas.
  • Citing sources shows the amount of research you've done.
  • Citing sources strengthens your work by lending outside support to your ideas.

Doesn't citing sources make my work seem less original?

Not at all. Citing sources actually helps your reader distinguish your ideas from those of your sources. This will emphasize the originality of your own work. It also gives you greater credibility because you are demonstrating your knowledge on the subject and your understanding of the work that's already been done by others on the subject.

When do I need to cite?

Whenever you borrow words or ideas from another source, you need to acknowledge that source. The following situations almost always require a citation:

  • Whenever you use quotes
  • Whenever you paraphrase
  • Whenever you use an idea that someone else has already expressed
  • Whenever you make specific reference to the work of another
  • Whenever someone else's work has been critical in developing your own ideas
  • How to tell the difference between Scholarly, Popular and Trade publications
  • Search engines vs. databases A video explaining the difference between using a search engine versus a database for scholarly research.
  • What is Peer Review? Video explaining peer review, (scholarly) articles in three minutes.
  • Citation Components APA and MLA aren't just your instructor's way of punishing you. These style guides ensure you give proper credit and avoid plagiarism.

The Limestone University OWL (online writing lab) is the virtual extension of the Writing Center on the main campus. The LU OWL offers live peer tutorial sessions to all students. On campus students may visit the Writing Lab in person. 

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  • Find Sources through the Library
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  • Evaluate, Write & Cite

Cite your sources

  • is the right thing to do  to give credit to those who had the idea
  • shows that you have read and understand  what experts have had to say about your topic
  • helps people find the sources  that you used in case they want to read more about the topic
  • provides   evidence  for your arguments
  • is professional and  standard practice   for students and scholars

What is a Citation?

A citation identifies for the reader the original source for an idea, information, or image that is referred to in a work.

  • In the body of a paper, the  in-text citation  acknowledges the source of information used.
  • At the end of a paper, the citations are compiled on a  References  or  Works Cited  list. A basic citation includes the author, title, and publication information of the source. 

Citation basics

From:  Lemieux  Library,  University  of Seattle 

Why Should You Cite?

Quoting Are you quoting two or more consecutive words from a source? Then the original source should be cited and the words or phrase placed in quotes. 

Paraphrasing If an idea or information comes from another source,  even if you put it in your own words , you still need to credit the source.  General vs. Unfamiliar Knowledge You do not need to cite material which is accepted common knowledge. If in doubt whether your information is common knowledge or not, cite it. Formats We usually think of books and articles. However, if you use material from web sites, films, music, graphs, tables, etc. you'll also need to cite these as well.

Plagiarism is presenting the words or ideas of someone else as your own without proper acknowledgment of the source. When you work on a research paper and use supporting material from works by others, it's okay to quote people and use their ideas, but you do need to correctly credit them. Even when you summarize or paraphrase information found in books, articles, or Web pages, you must acknowledge the original author.

Citation Style Help

Helpful links:

  • MLA ,  Works Cited : A Quick Guide (a template of core elements)
  • CSE  (Council of Science Editors)

For additional writing resources specific to styles listed here visit the  Purdue OWL Writing Lab

Citation and Bibliography Resources

Writing an annotated bibliography

  • How to Write an Annotated Bibliography
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The land acknowledgement used at UC Santa Cruz was developed in partnership with the Amah Mutsun Tribal Band Chairman and the Amah Mutsun Relearning Program at the UCSC Arboretum .

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A citation is a formal reference to a published or unpublished source that you consulted and obtained information from while writing your research paper. It refers to a source of information that supports a factual statement, proposition, argument, or assertion or any quoted text obtained from a book, article, web site, or any other type of material . In-text citations are embedded within the body of your paper and use a shorthand notation style that refers to a complete description of the item at the end of the paper. Materials cited at the end of a paper may be listed under the heading References, Sources, Works Cited, or Bibliography. Rules on how to properly cite a source depends on the writing style manual your professor wants you to use for the class [e.g., APA, MLA, Chicago, Turabian, etc.]. Note that some disciplines have their own citation rules [e.g., law].

Citations: Overview. OASIS Writing Center, Walden University; Research and Citation. The Writing Lab and The OWL. Purdue University; Citing Sources. University Writing Center, Texas A&M University.

Reasons for Citing Your Sources

Reasons for Citing Sources in Your Research Paper

English scientist, Sir Isaac Newton, once wrote, "If I have seen further, it is by standing on the shoulders of giants.”* Citations support learning how to "see further" through processes of intellectual discovery, critical thinking, and applying a deliberate method of navigating through the scholarly landscape by tracking how cited works are propagated by scholars over time and the subsequent ways this leads to the devarication of new knowledge.

Listed below are specific reasons why citing sources is an important part of doing good research.

  • Shows the reader where to find more information . Citations help readers expand their understanding and knowledge about the issues being investigated. One of the most effective strategies for locating authoritative, relevant sources about a research problem is to review materials cited in studies published by other authors. In this way, the sources you cite help the reader identify where to go to examine the topic in more depth and detail.
  • Increases your credibility as an author . Citations to the words, ideas, and arguments of scholars demonstrates that you have conducted a thorough review of the literature and, therefore, you are reporting your research results or proposing recommended courses of action from an informed and critically engaged perspective. Your citations offer evidence that you effectively contemplated, evaluated, and synthesized sources of information in relation to your conceptualization of the research problem.
  • Illustrates the non-linear and contested nature of knowledge creation . The sources you cite show the reader how you characterized the dynamics of prior knowledge creation relevant to the research problem and how you managed to effectively identify the contested relationships between problems and solutions proposed among scholars. Citations don't just list materials used in your study, they tell a story about how prior knowledge-making emerged from a constant state of creation, renewal, and transformation.
  • Reinforces your arguments . Sources cited in your paper provide the evidence that readers need to determine that you properly addressed the “So What?” question. This refers to whether you considered the relevance and significance of the research problem, its implications applied to creating new knowledge, and its importance for improving practice. In this way, citations draw attention to and support the legitimacy and originality of your own ideas.
  • Demonstrates that you "listened" to relevant conversations among scholars before joining in . Your citations tell the reader where you developed an understanding of the debates among scholars. They show how you educated yourself about ongoing conversations taking place within relevant communities of researchers before inserting your own ideas and arguments. In peer-reviewed scholarship, most of these conversations emerge within books, research reports, journal articles, and other cited works.
  • Delineates alternative approaches to explaining the research problem . If you disagree with prior research assumptions or you believe that a topic has been understudied or you find that there is a gap in how scholars have understood a problem, your citations serve as the source materials from which to analyze and present an alternative viewpoint or to assert that a different course of action should be pursued. In short, the materials you cite serve as the means by which to argue persuasively against long-standing assumptions propagated in prior studies.
  • Helps the reader understand contextual aspects of your research . Cited sources help readers understand the specific circumstances, conditions, and settings of the problem being investigated and, by extension, how your arguments can be fully understood and assessed. Citations place your line of reasoning within a specific contextualized framework based on how others have studied the problem and how you interpreted their findings in support of your overall research objectives.
  • Frames the development of concepts and ideas within the literature . No topic in the social and behavioral sciences rests in isolation from research that has taken place in the past. Your citations help the reader understand the growth and transformation of the theoretical assumptions, key concepts, and systematic inquiries that emerged prior to your engagement with the research problem.
  • Underscores what sources were most important to you . Your citations represent a set of choices made about what you determined to be the most important sources for understanding the topic. They not only list what you discovered, but why it matters and how the materials you chose to cite fit within the broader context of your research design and arguments. As part of an overall assessment of the study’s validity and reliability , the choices you make also helps the reader determine what research may have been excluded.
  • Provides evidence of interdisciplinary thinking . An important principle of good research is to extend your review of the literature beyond the predominant disciplinary space where scholars have examined a topic. Citations provide evidence that you have integrated epistemological arguments, observations, and/or the methodological strategies from other disciplines into your paper, thereby demonstrating that you understand the complex, interconnected nature of contemporary research problems.
  • Supports critical thinking and independent learning . Evaluating the authenticity, reliability, validity, and originality of prior research is an act of interpretation and introspective reasoning applied to assessing whether a source of information will contribute to understanding the problem in ways that are persuasive and align with your overall research objectives. Reviewing and citing prior studies represents a deliberate act of critically scrutinizing each source as part of your overall assessment of how scholars have confronted the research problem.
  • Honors the achievements of others . As Susan Blum recently noted,** citations not only identify sources used, they acknowledge the achievements of scholars within the larger network of research about the topic. Citing sources is a normative act of professionalism within academe and a way to highlight and recognize the work of scholars who likely do not obtain any tangible benefits or monetary value from their research endeavors.

*Vernon. Jamie L. "On the Shoulder of Giants." American Scientist 105 (July-August 2017): 194.

**Blum, Susan D. "In Defense of the Morality of Citation.” Inside Higher Ed , January 29, 2024.

Aksnes, Dag W., Liv Langfeldt, and Paul Wouters. "Citations, Citation Indicators, and Research Quality: An Overview of Basic Concepts and Theories." Sage Open 9 (January-March 2019): https://doi.org/10.1177/2158244019829575; Blum, Susan Debra. My Word!: Plagiarism and College Culture . Ithaca, NY: Cornell University Press, 2009; Bretag, Tracey., editor. Handbook of Academic Integrity . Singapore: Springer Singapore, 2020; Ballenger, Bruce P. The Curious Researcher: A Guide to Writing Research Papers . 7th edition. Boston, MA: Pearson, 2012; D'Angelo, Barbara J. "Using Source Analysis to Promote Critical Thinking." Research Strategies 18 (Winter 2001): 303-309; Mauer, Barry and John Venecek. “Scholarship as Conversation.” Strategies for Conducting Literary Research, University of Central Florida, 2021; Why Cite? Poorvu Center for Teaching and Learning, Yale University; Citing Information. The Writing Center. University of North Carolina; Harvard Guide to Using Sources. Harvard College Writing Program. Harvard University; Newton, Philip. "Academic Integrity: A Quantitative Study of Confidence and Understanding in Students at the Start of Their Higher Education."  Assessment and Evaluation in Higher Education 41 (2016): 482-497; Referencing More Effectively. Academic Skills Centre. University of Canberra; Using Sources. Yale College Writing Center. Yale University; Vosburgh, Richard M. "Closing the Academic-practitioner Gap: Research Must Answer the “SO WHAT” Question." H uman Resource Management Review 32 (March 2022): 100633; When and Why to Cite Sources. Information Literacy Playlists, SUNY, Albany Libraries.

Structure and Writing Style

Referencing your sources means systematically showing what information or ideas you acquired from another author’s work, and identifying where that information come from . You must cite research in order to do research, but at the same time, you must delineate what are your original thoughts and ideas and what are the thoughts and ideas of others. Citations help achieve this. Procedures used to cite sources vary among different fields of study. If not outlined in your course syllabus or writing assignment, always speak with your professor about what writing style for citing sources should be used for the class because it is important to fully understand the citation style to be used in your paper, and to apply it consistently. If your professor defers and tells you to "choose whatever you want, just be consistent," then choose the citation style you are most familiar with or that is appropriate to your major [e.g., use Chicago style if its a history class; use APA if its an education course; use MLA if it is literature or a general writing course].

GENERAL GUIDELINES

1. Are there any reasons I should avoid referencing other people's work? No. If placed in the proper context, r eferencing other people's research is never an indication that your work is substandard or lacks originality. In fact, the opposite is true. If you write your paper without adequate references to previous studies, you are signaling to the reader that you are not familiar with the literature on the topic, thereby, undermining the validity of your study and your credibility as a researcher. Including references in academic writing is one of the most important ways to demonstrate your knowledge and understanding of how the research problem has been addressed. It is the intellectual packaging around which you present your thoughts and ideas to the reader.

2. What should I do if I find out that my great idea has already been studied by another researcher? It can be frustrating to come up with what you believe is a great topic only to find that it's already been thoroughly studied. However, do not become frustrated by this. You can acknowledge the prior research by writing in the text of your paper [see also Smith, 2002], then citing the complete source in your list of references. Use the discovery of prior studies as an opportunity to demonstrate the significance of the problem being investigated and, if applicable, as a means of delineating your analysis from those of others [e.g., the prior study is ten years old and doesn't take into account new variables]. Strategies for responding to prior research can include: stating how your study updates previous understandings about the topic, offering a new or different perspective, applying a different or innovative method of data gathering, and/or describing a new set of insights, guidelines, recommendations, best practices, or working solutions.

3. What should I do if I want to use an adapted version of someone else's work? You still must cite the original work. For example, maybe you are using a table of statistics from a journal article published in 1996 by author Smith, but you have altered or added new data to it. Reference the revised chart, such as, [adapted from Smith, 1996], then cite the complete source in your list of references. You can also use other terms in order to specify the exact relationship between the original source and the version you have presented, such as, "based on data from Smith [1996]...," or "summarized from Smith [1996]...." Citing the original source helps the reader locate where the information was first presented and under what context it was used as well as to evaluate how effectively you applied it to your own research.

4. What should I do if several authors have published very similar information or ideas? You can indicate that the idea or information can be found in the works of others by stating something similar to the following example: "Though many scholars have applied rational choice theory to understanding economic relations among nations [Smith, 1989; Jones, 1991; Johnson, 1994; Anderson, 2003], little attention has been given to applying the theory to examining the influence of non-governmental organizations in a globalized economy." If you only reference one author or only the most recent study, then your readers may assume that only one author has published on this topic, or more likely, they will conclude that you have not conducted a thorough literature review. Referencing all relevant authors of prior studies gives your readers a clear idea of the breadth of analysis you conducted in preparing to study the research problem. If there has been a significant number of prior studies on the topic, describe the most comprehensive and recent works because they will presumably discuss and reference the older studies. However, note in your review of the literature that there has been significant scholarship devoted to the topic so the reader knows that you are aware of the numerous prior studies.

5. What if I find exactly what I want to say in the writing of another researcher? In the social sciences, the rationale in duplicating prior research is generally governed by the passage of time, changing circumstances or conditions, or the emergence of variables that necessitate a new investigation . If someone else has recently conducted a thorough investigation of precisely the same research problem that you intend to study, then you likely will have to revise your topic, or at the very least, review this literature to identify something new to say about the problem. However, if it is someone else's particularly succinct expression, but it fits perfectly with what you are trying to say, then you can quote from the author directly, referencing the source. Identifying an author who has made the exact same point that you want to make can be an opportunity to add legitimacy to, as well as reinforce the significance of, the research problem you are investigating. The key is to build on that idea in new and innovative ways. If you are not sure how to do this, consult with a librarian .

6. Should I cite a source even if it was published long ago? Any source used in writing your paper should be cited, regardless of when it was written. However, in building a case for understanding prior research about your topic, it is generally true that you should focus on citing more recently published studies because they presumably have built upon the research of older studies. When referencing prior studies, use the research problem as your guide when considering what to cite. If a study from forty years ago investigated the same topic, it probably should be examined and considered in your list of references because the research may have been foundational or groundbreaking at the time, even if its findings are no longer relevant to current conditions or reflect current thinking [one way to determine if a study is foundational or groundbreaking is to examine how often it has been cited in recent studies using the "Cited by" feature of Google Scholar ]. However, if an older study only relates to the research problem tangentially or it has not been cited in recent studies, then it may be more appropriate to list it under further readings .

NOTE:   In any academic writing, you are required to identify which ideas, facts, thoughts, concepts, or declarative statements are yours and which are derived from the research of others. The only exception to this rule is information that is considered to be a commonly known fact [e.g., "George Washington was the first president of the United States"] or a statement that is self-evident [e.g., "Australia is a country in the Global South"]. Appreciate, however, that any "commonly known fact" is culturally constructed and shaped by social and aesthetical biases . If you are in doubt about whether or not a fact is considered to be widely understood knowledge, provide a supporting citation, or, ask your professor for clarification about how the statement should be cited.

Ballenger, Bruce P. The Curious Researcher: A Guide to Writing Research Papers . 7th edition. Boston, MA: Pearson, 2012; Blum, Susan Debra. My Word!: Plagiarism and College Culture . Ithaca, NY: Cornell University Press, 2009; Bretag, Tracey., editor. Handbook of Academic Integrity . Singapore: Springer Singapore, 2020; Carlock, Janine. Developing Information Literacy Skills: A Guide to Finding, Evaluating, and Citing Sources . Ann Arbor, MI: University of Michigan Press, 2020; Harvard Guide to Using Sources. Harvard College Writing Program. Harvard University; How to Cite Other Sources in Your Paper. The Structure, Format, Content, and Style of a Journal-Style Scientific Paper. Department of Biology. Bates College; Lunsford, Andrea A. and Robert Connors; The St. Martin's Handbook . New York: St. Martin's Press, 1989; Mills, Elizabeth Shown. Evidence Explained: Citing History Sources from Artifacts to Cyberspace . 3rd edition. Baltimore, MD: Genealogical Publishing Company, 2015; Research and Citation Resources. The Writing Lab and The OWL. Purdue University; Writing Tutorial Services, Center for Innovative Teaching and Learning. Indiana University; Why Cite? Poorvu Center for Teaching and Learning, Yale Univeraity.

Other Citation Research Guides

The following USC Libraries research guide can help you properly cite sources in your research paper:

  • Citation Guide

The following USC Libraries research guide offers basic information on using images and media in research:

Listed below are particularly well-done and comprehensive websites that provide specific examples of how to cite sources under different style guidelines.

  • Purdue University Online Writing Lab
  • Southern Cross University Harvard Referencing Style
  • University of Wisconsin Writing Center

This is a useful guide concerning how to properly cite images in your research paper.

  • Colgate Visual Resources Library, Citing Images

This guide provides good information on the act of citation analysis, whereby you count the number of times a published work is cited by other works in order to measure the impact of a publication or author.

Measuring Your Impact: Impact Factor, Citation Analysis, and other Metrics: Citation Analysis [Sandy De Groote, University of Illinois, Chicago]

Automatic Citation Generators

The links below lead to systems where you can type in your information and have a citation compiled for you. Note that these systems are not foolproof so it is important that you verify that the citation is correct and check your spelling, capitalization, etc. However, they can be useful in creating basic types of citations, particularly for online sources.

  • BibMe -- APA, MLA, Chicago, and Turabian styles
  • DocsCite -- for citing government publications in APA or MLA formats
  • EasyBib -- APA, MLA, and Chicago styles
  • Son of Citation Machine -- APA, MLA, Chicago, and Turabian styles

NOTE:   Many companies that create the research databases the USC Libraries subscribe to, such as ProQuest , include built-in citation generators that help take the guesswork out of how to properly cite a work. When available, you should always utilize these features because they not only generate a citation to the source [e.g., a journal article], but include information about where you accessed the source [e.g., the database].

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  • URL: https://libguides.usc.edu/writingguide

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Course & Subject Guides

Citation styles: apa, mla, chicago, turabian, ieee.

  • APA 7th Edition
  • Turabian 9th
  • Writing & Citing Help
  • Understanding Plagiarism

Quick Links

Listed below are a few quick links to resources that will aid you in citing sources.

  • Sign up for a Mendeley, EndNote, or Zotero training class.
  • APA 7th Edition Published in October 2019. Visit this page for links to resources and examples.
  • MLA Need help with citing MLA style? Find information here along with links to books in PittCat and free online resources.
  • Chicago/Turabian Need help with citing Chicago/Turabian style? Find examples here along with links to the online style manual and free online resources.

Getting Started: How to use this guide

This LibGuide was designed to provide you with assistance in citing your sources when writing an academic paper.

There are different styles which format the information differently. In each tab, you will find descriptions of each citation style featured in this guide along with links to online resources for citing and a few examples.

What is a citation and citation style?

A citation is a way of giving credit to individuals for their creative and intellectual works that you utilized to support your research. It can also be used to locate particular sources and combat plagiarism. Typically, a citation can include the author's name, date, location of the publishing company, journal title, or DOI (Digital Object Identifier).

A citation style dictates the information necessary for a citation and how the information is ordered, as well as punctuation and other formatting.

How to do I choose a citation style?

There are many different ways of citing resources from your research. The citation style sometimes depends on the academic discipline involved. For example:

  • APA (American Psychological Association) is used by Education, Psychology, and Sciences
  • MLA (Modern Language Association) style is used by the Humanities
  • Chicago/Turabian style is generally used by Business, History, and the Fine Arts

*You will need to consult with your professor to determine what is required in your specific course.

Click the links below to find descriptions of each style along with a sample of major in-text and bibliographic citations, links to books in PittCat, online citation manuals, and other free online resources.

  • APA Citation Style
  • MLA Citation Style
  • Chicago/Turabian Citation Style
  • Tools for creating bibliographies (CItation Managers)

Writing Centers

Need someone to review your paper? Visit the Writing Center or Academic Success Center on your campus.

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Quetext

What is a Citation in Writing? Definition, Examples

  • Posted on June 7, 2023

Writing is not only about expressing your own thoughts but also about using information from other sources to support them. But how do you show your readers where you got that information from? 

That’s where citations come in. Citations are a way of giving credit to the original authors and avoiding plagiarism. They also help your readers to find the original sources if they want to learn more. 

A proper citation includes:

  • The author’s name.
  • The title of the source.
  • The publication date.
  • The page number.
  • The references page is where all the sources are listed.

You can use different citation styles depending on your writing purpose and audience.

You can also visit a writing lab to get help with citations and other aspects of writing. Citations can make your writing more credible and authoritative because they show that you have done the research and used reliable sources. They can also help search engines to rank your writing higher in the search results.

By the end of this article, you will have gained valuable insights into crafting accurate citations that adhere to formatting guidelines while effectively avoiding plagiarism throughout your writing process.

What is a Citation?

A citation is a way of giving credit to the source of information that you use in your writing. It shows your readers where you got the information from and how they can find it. It also helps you avoid plagiarism, which is copying someone else’s work without permission. A citation usually includes the following information:

  • Original author information : This tells your readers who wrote the original source that you are using. For example, if you are citing a journal article, you would include the author’s name and affiliation.
  • Date of publication of your copy : This tells your readers when you accessed the source that you are using. For example, if you are citing a web page, you would include the date that you visited the page.
  • Year of publication of original copy : This tells your readers when the original source that you are using was published. For example, if you are citing a book, you would include the year that the book was printed.
  • Page numbers you are using : This tells your readers which part of the source that you are using. For example, if you are citing a chapter in a book, you would include the page numbers that you are quoting or paraphrasing.
  • The material you are using in the citation : This tells your readers what kind of information you are using from the source. For example, if you are citing a quote , a paraphrase, or a summary.

You should include citations in the text of your paper and on a separate references page at the end of your paper. 

Why is it Important to Cite Original Sources?

Citing original sources is important for several reasons. First, it shows respect and honesty to the original authors and sources you use, and it acknowledges their contribution and gives them credit for their work. 

Second, it helps you avoid plagiarism , which is using someone else’s work as your own without permission. Plagiarism is a serious academic offense that can negatively affect your reputation and career. 

Third, it shows the credibility and quality of your own work. It demonstrates that you have researched and used reliable and relevant sources to support your arguments. It also indicates that you have followed the writing style and format of your discipline and source type. 

Finally, it helps your readers to find and evaluate your sources. It provides them with a reference list where they can access the original sources if they want to learn more or check your information.

When Do You Need to Cite?

You must cite whenever you borrow ideas, words, or images from another source. Some examples of when you need to cite are:

  • When you borrow an idea that someone else has already presented in their work
  • When you use a direct quote from a source, using the same words as the author
  • When you restate the author’s words in your own words
  • When you mention a specific detail from the work of another, such as the title, date, or page number
  • When you rely on the research and work of another to create your own ideas or arguments

You can cite your sources in different ways, such as using parentheses with the author’s last name and the year of publication or using footnotes or endnotes. You can also use Libguides to help you with citing your sources correctly for your research paper.

The Most Common Citation Style Guides

In today’s academic and professional world, various citation styles are used to appropriately credit the original authors of the sources referenced in a piece of writing. These citation style guides provide standardized formats for referencing sources, ensuring consistency and clarity across different disciplines.

MLA (Modern Language Association) Style

The MLA citations are popular among humanities scholars like literature and language researchers and use parenthetical citations within text along with an alphabetically arranged Works Cited page at the end.

APA (American Psychological Association) Style

APA citations are commonly used in social sciences such as psychology, education, and sociology. It emphasizes the author-date system for in-text citations and includes a detailed reference list at the end of the document.

In-Text Citation

In-text citations are references in your work that show the source of other authors’ ideas and words. They help readers find more information and avoid plagiarism. There are different in-text citation formats, such as parenthetical and narrative. They usually include the author’s name and publication year, and sometimes page numbers. They should match your reference list, which has all the sources you used.

Chicago Manual of Style

Chicago-style citations are a way of referencing sources in writing, especially in the humanities. They are based on the guidelines of The Chicago Manual of Style (CMOS), a style guide for American English. There are two types of Chicago-style citations: notes and bibliography and author-date. Notes and bibliography use footnotes or endnotes and a bibliography to cite sources, while author-date use parenthetical references and a reference list. Chicago-style citations help writers avoid plagiarism and show respect to the original authors and sources.

Turabian Style

Chicago/Turabian style, favored by historians and other fields that use extensive primary source material, offers two options: notes-bibliography system or author-date system, depending on discipline-specific preferences.

In conclusion, a citation is an essential aspect of writing that helps to acknowledge the original sources used in creating content. It ensures that credit is given where it’s due and prevents plagiarism. Knowing when to cite and which citation style guide to use can be crucial for businesses and marketing teams looking to create high-quality content.

Citing sources can be challenging, but you don’t have to do it alone. Quetext is a trusted tool and partner that can help you avoid plagiarism and generate quality citations. Quetext has a citation generator that can create citations in various styles, such as APA, MLA, Chicago, and more. You can also use Quetext to check your work for plagiarism and improve your writing skills. 

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APA Citation Style

Citation examples.

  • Paper Format
  • Style and Grammar Guidelines
  • Citation Management Tools
  • What's New in the 7th Edition?
  • APA Style References Guidelines from the American Psychological Association
  • APA Style (OWL - Online Writing Lab, Purdue University)
  • Common Reference Examples Handout
  • Journal Article
  • Magazine Article
  • Newspaper Article
  • Edited Book Chapter
  • Dictionary Entry
  • Government Report
  • YouTube Video
  • Facebook Post
  • Webpage on a Website
  • Supplemental Reference Examples
  • Archival Documents and Collections

Parenthetical citations:  (Grady et al., 2019; Jerrentrup et al., 2018)

Narrative citations:  Grady et al. (2019) and Jerrentrup et al. (2018)

  • If a journal article has a DOI, include the DOI in the reference.
  • If the journal article does not have a DOI and is from an academic research database, end the reference after the page range (for an explanation of why, see the  database information  page). The reference in this case is the same as for a print journal article.
  • Do not include database information in the reference unless the journal article comes from a database that publishes original, proprietary content, such as UpToDate (see an example on the  database information  page).
  • If the journal article does not have a DOI but does have a URL that will resolve for readers (e.g., it is from an online journal that is not part of a database), include the URL of the article at the end of the reference.
  • If the journal article has an article number instead of a page range, include the article number instead of the page range (as shown in the Jerrentrup et al. example).

Parenthetical citations:  (Rabinowitz, 2019; Sapolsky, 2017)

Narrative citations:  Rabinowitz (2019) and Sapolsky (2017)

  • If the book includes a DOI, include the DOI in the reference after the publisher name.
  • Do not include the publisher location.
  • If the book does not have a DOI and comes from an academic research database, end the book reference after the publisher name. Do not include  database information  in the reference. The reference in this case is the same as for a print book.

Parenthetical citations:  (Schaefer & Shapiro, 2019; Schulman, 2019)

Narrative citations:  Schaefer and Shapiro (2019) and Schulman (2019)

  • If a magazine article has a DOI, include the DOI in the reference.
  • If the magazine article does not have a DOI and is from an academic research database, end the reference after the page range. Do not include  database information  in the reference. The reference in this case is the same as for a print magazine article.
  • If the magazine article does not have a DOI but does have a URL that will resolve for readers (e.g., it is from an online magazine that is not part of a database), include the URL of the article at the end of the reference.
  • If the magazine article does not have volume, issue, and/or page numbers (e.g., because it is from an online magazine), omit the missing elements from the reference (as in the Schulman example).

Parenthetical citation:  (Carey, 2019)

Narrative citation:  Carey (2019)

  • If the newspaper article is from an academic research database, end the reference after the page range. Do not include  database information  in the reference. The reference in this case is the same as for a print newspaper article.
  • If the newspaper article has a URL that will resolve for readers (e.g., it is from an online newspaper), include the URL of the article at the end of the reference.
  • If the newspaper article does not have volume, issue, and/or page numbers (e.g., because it is from an online newspaper), omit the missing elements from the reference, as shown in the example.
  • If the article is from a news website (e.g., CNN, HuffPost)—one that does not have an associated daily or weekly newspaper—use the format for a  webpage on a website  instead.

Parenthetical citation:  (Aron et al., 2019)

Narrative citation:  Aron et al. (2019)

  • If the edited book chapter includes a DOI, include the chapter DOI in the reference after the publisher name.
  • If the edited book chapter does not have a DOI and comes from an academic research database, end the edited book chapter reference after the publisher name. Do not include  database information  in the reference. The reference in this case is the same as for a print edited book chapter.
  • Do not create references for chapters of authored books. Instead, write a reference for the whole book and cite the chapter in the text if desired (e.g., Kumar, 2017, Chapter 2).

Parenthetical citation:  (Merriam-Webster, n.d.)

Narrative citation:  Merriam-Webster (n.d.)

  • Because entries in  Merriam-Webster’s Dictionary  are updated over time and are not archived, include a  retrieval date  in the reference.
  • Merriam-Webster is both the author and the publisher, so the name appears in the author element only to avoid repetition.
  • To quote a dictionary definition, view the pages on quotations and  how to quote works without page numbers  for guidance. Additionally, here is an example:  Culture  refers to the “customary beliefs, social forms, and material traits of a racial, religious, or social group” (Merriam-Webster, n.d., Definition 1a).

Parenthetical citation:  (National Cancer Institute, 2019)

Narrative citation:  National Cancer Institute (2019)

The specific agency responsible for the report appears as the author. The names of parent agencies not present in the  group author name  appear in the source element as the publisher. This creates concise in-text citations and complete reference list entries.

Parenthetical citation:  (Harvard University, 2019)

Narrative citation:  Harvard University (2019)

  • Use the name of the account that uploaded the video as the author.
  • If the account did not actually create the work, explain this in the text if it is important for readers to know. However, if that would mean citing a source that appears unauthoritative, you might also look for the author’s YouTube channel, official website, or other social media to see whether the same video is available elsewhere.

Parenthetical citations:  (APA Databases, 2019; Gates, 2019)

Narrative citations:  APA Databases (2019) and Gates (2019)

  • Present the name of the individual or group author the same as you would for any other reference. Then provide the Twitter handle (beginning with the @ sign) in square brackets, followed by a period.
  • Provide the first 20 words of the tweet as the title. Count a URL, a hashtag, or an emoji as one word each, and include them in the reference if they fall within the first 20 words.
  • If the tweet includes an image, a video, a poll, or a thumbnail image with a link, indicate that in brackets after the title: [Image attached], [Video attached], [Thumbnail with link attached].
  • The same format used for Twitter is also used for Instagram.  

Parenthetical citation:  (News From Science, 2019)

Narrative citation:  News From Science (2019)

  • Provide the first 20 words of the Facebook post as the title. Count a URL or other link, a hashtag, or an emoji as one word each, and include them in the reference if they fall within the first 20 words. 
  • If a status update includes images, videos, thumbnail links to outside sources, or content from another Facebook post (such as when sharing a link), indicate that in square brackets.

Parenthetical citations:  (Fagan, 2019; National Institute of Mental Health, 2018; Woodyatt, 2019; World Health Organization, 2018)

Narrative citations:  Fagan (2019), National Institute of Mental Health (2018), Woodyatt (2019), and World Health Organization (2018)

  • Provide as specific a  date  as is available on the webpage. This might be a year only; a year and month; or a year, month, and day.
  • Italicize the title of a webpage.
  • When the author of the webpage and the publisher of the website are the same, omit the publisher name to avoid repetition (as in the World Health Organization example).
  • When contents of a page are meant to be updated over time but are not archived, include a  retrieval date  in the reference (as in the Fagan example).
  • Use the webpage on a website format for articles from news websites such as CNN and HuffPost (these sites do not have associated daily or weekly newspapers). Use the  newspaper article category  for articles from newspaper websites such as  The New York Times  or  The Washington Post .
  • Create a reference to an open educational resources (OER) page only when the materials are available for download directly (i.e., the materials are on the page and/or can be downloaded as PDFs or other files). If you are directed to another website, create a reference to the specific webpage on that website where the materials can be retrieved. Use this format for material in any OER repository, such as OER Commons, OASIS, or MERLOT.
  • Do not create a reference or in-text citation for a whole website. To mention a website in general, and not any particular information on that site, provide the name of the website in the text and include the URL in parentheses. For example, you might mention that you used a website to create a survey.

The following supplemental example references are mention in the  Publication Manual:

  • retracted journal or magazine article
  • edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM)
  • edition of the International Statistical Classification of Diseases and Related Health Problems (ICD)
  • religious work
  • annotated religious work

Archival document and collections are not presented in the  APA Publication Manual, Seventh Edition . This content is available only on the APA Style website .  This guidance has been expanded from the 6th edition.

Archival sources include letters, unpublished manuscripts, limited-circulation brochures and pamphlets, in-house institutional and corporate documents, clippings, and other documents, as well as such nontextual materials as photographs and apparatus, that are in the personal possession of an author, form part of an institutional collection, or are stored in an archive such as the Archives of the History of American Psychology at the University of Akron or the APA Archives. For any documents like these that are available on the open web or via a database (subscription or nonsubscription), follow the reference templates shown in Chapter 10 of the Publication Manual.

The general format for the reference for an archival work includes the author, date, title, and source. The reference examples shown on this page may be modified for collections requiring more or less specific information to locate materials, for different types of collections, or for additional descriptive information (e.g., a translation of a letter). Authors may choose to list correspondence from their own personal collections, but correspondence from other private collections should be listed only with the permission of the collector.

Keep in mind the following principles when creating references to archival documents and collections:

  • As with any reference, the purpose is to direct readers to the source, despite the fact that only a single copy of the document may be available and readers may have some difficulty actually seeing a copy.
  • Include as much information as is needed to help locate the item with reasonable ease within the repository. For items from collections with detailed finding aids, the name of the collection may be sufficient; for items from collections without finding aids, more information (e.g., call number, box number, file name or number) may be necessary to help locate the item.
  • If several letters are cited from the same collection, list the collection as a reference and provide specific identifying information (author, recipient, and date) for each letter in the in-text citations (see Example 3).
  • Use square brackets to indicate information that does not appear on the document.
  • Use “ca.” (circa) to indicate an estimated date (see Example 5).
  • Use italics for titles of archival documents and collections; if the work does not have a title, provide a description in square brackets without italics.
  • Separate elements of the source (e.g., the name of a repository, library, university or archive, and the location of the university or archive) with commas. End the source with a period.
  • If a publication of limited circulation is available in libraries, the reference may be formatted as usual for published material, without the archival source.
  • Note that private letters (vs. those in an archive or repository) are considered personal communications and cited in the text only.

1. Letter from a repository

Frank, L. K. (1935, February 4). [Letter to Robert M. Ogden]. Rockefeller Archive Center (GEB Series 1.3, Box 371, Folder 3877), Tarrytown, NY, United States.

  • Parenthetical citation: (Frank, 1935)
  • Narrative citation: Frank (1935)
  • Because the letter does not have a title, provide a description in square brackets.

2. Letter from a private collection

Zacharius, G. P. (1953, August 15). [Letter to William Rickel (W. Rickel, Trans.)]. Copy in possession of Hendrika Vande Kemp.

  • Parenthetical citation: (Zacharius, 1953)
  • Narrative citation: Zacharius (1953)
  • In this example, Hendrika Vande Kemp is either the author of the paper or the author of the paper has received permission from Hendrika Vande Kemp to cite a letter in Vande Kemp’s private collection in this way. Otherwise, cite a private letter as a  personal communication .

3. Collection of letters from an archive

Allport, G. W. (1930–1967). Correspondence. Gordon W. Allport Papers (HUG 4118.10), Harvard University Archives, Cambridge, MA, United States.

  • Parenthetical citation: (Allport, 1930–1967)
  • Narrative citation: Allport (1930–1967)

To cite specific letters in the text, provide the author and range of years as shown in the reference list entry, plus details about who wrote the specific letter to whom and when the specific letter was written.

  • Parenthetical citation: (Allport, 1930–1967, G. Boring to Allport, December 26, 1937)
  • Narrative citation: Allport (1930–1967, Allport to G. Boring, March 1, 1939)
  • Use the parenthetical citation format to cite a letter that E. G. Boring wrote to Allport because Allport is the author in the reference. Use either the parenthetical or narrative citation format to cite letters that Allport wrote.

4. Unpublished papers, lectures from an archive or personal collection

Berliner, A. (1959). Notes for a lecture on reminiscences of Wundt and Leipzig. Anna Berliner Memoirs (Box M50), Archives of the History of American Psychology, University of Akron, Akron, OH, United States.

  • Parenthetical citation: (Berliner, 1959)
  • Narrative citation: Berliner (1959)

5. Archival/historical source for which the author and/or date is known or is reasonably certain but not stated on the document

Allport, A. (presumed). (ca. 1937). Marion Taylor today—by the biographer [Unpublished manuscript]. Marion Taylor Papers, Schlesinger Library, Radcliffe College, Cambridge, MA, United States.

  • Parenthetical citation: (Allport, ca. 1937)
  • Narrative citation: Allport (ca. 1937)
  • Because the author is reasonably certain but not stated on the document, place the word “presumed” in parentheses after the name, followed by a period.
  • Because the date is reasonably certain but not stated on the document, the abbreviation “ca.” (which stands for “circa”) appears before the year in parentheses.

6. Archival source with group author

Subcommittee on Mental Hygiene Personnel in School Programs. (1949, November 5–6). Meeting of Subcommittee on Mental Hygiene Personnel in School Programs. David Shakow Papers (M1360), Archives of the History of American Psychology, University of Akron, Akron, OH, United States.

  • Parenthetical citation: (Subcommittee on Mental Hygiene Personnel in School Programs, 1949)
  • Narrative citation: Subcommittee on Mental Hygiene Personnel in School Programs (1949)

7. Interview recorded and available in an archive

Smith, M. B. (1989, August 12). Interview by C. A. Kiesler [Tape recording]. President’s Oral History Project, American Psychological Association, APA Archives, Washington, DC, United States.

  • Parenthetical citation: (Smith, 1989)
  • Narrative citation: Smith (1989)
  • For interviews and oral histories recorded in an archive, list the interviewee as the author. Include the interviewer’s name in the description.

8. Transcription of a recorded interview, no recording available

Sparkman, C. F. (1973). An oral history with Dr. Colley F. Sparkman/Interviewer: Orley B. Caudill. Mississippi Oral History Program (Vol. 289), University of Southern Mississippi, Hattiesburg, MS, United States.

  • Parenthetical citation: (Sparkman, 1973)
  • Narrative citation: Sparkman (1973)

9. Newspaper article clipping, historical, in personal collection

Psychoanalysis institute to open. (1948, September 18). [Clipping from an unidentified Dayton, OH, United States, newspaper]. Copy in possession of author.

  • Parenthetical citation: (“Psychoanalysis Institute to Open,” 1948)
  • Narrative citation: “Psychoanalysis Institute to Open” (1948)
  • Use this format only if you are the person who is in possession of the newspaper clipping.

10. Historical publication of limited circulation

Sci-Art Publishers. (1935). Sci-Art publications [Brochure]. Roback Papers (HUGFP 104.50, Box 2, Folder “Miscellaneous Psychological Materials”), Harvard University Archives, Cambridge, MA, United States.

  • Parenthetical citation: (Sci-Art Publishers, 1935)
  • Narrative citation: Sci-Art Publishers (1935)

11. Archived photographs, no author and no title

[Photographs of Robert M. Yerkes]. (ca. 1917–1954). Robert Mearns Yerkes Papers (Box 137, Folder 2292), Manuscripts and Archives, Yale University Library, New Haven, CT, United States.

  • Parenthetical citation: ([Photographs of Robert M. Yerkes], ca. 1917–1954)
  • Narrative citation: [Photographs of Robert M. Yerkes] (ca. 1917–1954)
  • Because the archived photographs do not have a title, provide a bracketed description instead.
  • Because the archived photographs do not have an author, move the bracketed description to the author position of the reference.

12. Microfilm

U.S. Census Bureau. (1880). 1880 U.S. census: Defective, dependent, and delinquent classes schedule: Virginia [Microfilm]. NARA Microfilm Publication T1132 (Rolls 33–34), National Archives and Records Administration, Washington, DC, United States.

  • Parenthetical citation: (U.S. Census Bureau, 1880)
  • Narrative citation: U.S. Census Bureau (1880)

Read the full APA guidelines on citing ChatGPT 

OpenAI. (2023).  ChatGPT  (Mar 14 version) [Large language model].  https://chat.openai.com/chat

  • Parenthetical citation:  (OpenAI, 2023)
  • Narrative citation:  OpenAI (2023)

Author:  The author of the model is OpenAI.

Date:  The date is the year of the version you used. Following the template in Section 10.10, you need to include only the year, not the exact date. The version number provides the specific date information a reader might need.

Title:  The name of the model is “ChatGPT,” so that serves as the title and is italicized in your reference, as shown in the template. Although OpenAI labels unique iterations (i.e., ChatGPT-3, ChatGPT-4), they are using “ChatGPT” as the general name of the model, with updates identified with version numbers.

The version number is included after the title in parentheses. The format for the version number in ChatGPT references includes the date because that is how OpenAI is labeling the versions. Different large language models or software might use different version numbering; use the version number in the format the author or publisher provides, which may be a numbering system (e.g., Version 2.0) or other methods.

Bracketed text  is used in references for additional descriptions when they are needed to help a reader understand what’s being cited. References for a number of common sources, such as journal articles and books, do not include bracketed descriptions, but things outside of the typical peer-reviewed system often do. In the case of a reference for ChatGPT, provide the descriptor “Large language model” in square brackets. OpenAI describes ChatGPT-4 as a “large multimodal model,” so that description may be provided instead if you are using ChatGPT-4. Later versions and software or models from other companies may need different descriptions, based on how the publishers describe the model. The goal of the bracketed text is to briefly describe the kind of model to your reader.

Source:  When the publisher name and the author name are the same, do not repeat the publisher name in the source element of the reference, and move directly to the URL. This is the case for ChatGPT. The URL for ChatGPT is  https://chat.openai.com/chat . For other models or products for which you may create a reference, use the URL that links as directly as possible to the source (i.e., the page where you can access the model, not the publisher’s homepage).

What to include and what to exclude

Works included in a reference list.

The reference list provides a reliable way for readers to identify and locate the works cited in a paper. APA Style papers generally include reference lists, not  bibliographies.

In general, each work cited in the text must appear in the reference list, and each work in the reference list must be cited in the text. Check your work carefully before submitting your manuscript or course assignment to ensure no works cited in the text are missing from the reference list and vice versa, with only the following exceptions.

Works Excluded From a Reference List

There are a few kinds of works that are not included in a reference list. Usually a work is not included because readers cannot recover it or because the mention is so broad that readers do not need a reference list entry to understand the use.

Information on works included in a reference list is covered in Sections 2.12 and 8.4 of the  APA Publication Manual, Seventh Edition

*This guidance has been expanded from the 6th edition.*

  • Personal communications  such as emails, phone calls, or text messages are cited in the text only, not in the reference list, because readers cannot retrieve personal communications.
  • General mentions of whole websites, whole periodicals, and common software and apps in the text do not require in-text citations or reference list entries because the use is broad and the source is familiar.
  • The source of an epigraph does not usually appear in the reference list unless the work is a scholarly book or journal. For example, if you open the paper with an inspirational quotation by a famous person, the source of the quotation does not appear in the reference list because the quotation is meant to set the stage for the work, not substantiate a key point.   
  • Quotations from research participants in a study you conducted can be presented and discussed in the text but do not need citations or reference list entries. Citations and reference list entries are not necessary because the quotations are part of your original research. They could also compromise participants’ confidentiality, which is an ethical violation.
  • References included in a meta-analysis, which are marked with an asterisk in the reference list, may be cited in the text (or not) at the author’s discretion. This exception is relevant only to authors who are conducting a meta-analysis.

DOIs and URLs

The DOI or URL is the final component of a reference list entry. Because so much scholarship is available and/or retrieved online, most reference list entries end with either a DOI or a URL.

  • A DOI is a unique alphanumeric string that identifies content and provides a persistent link to its location on the internet. DOIs can be found in database records and the reference lists of published works.
  • A URL specifies the location of digital information on the internet and can be found in the address bar of your internet browser. URLs in references should link directly to the cited work when possible.

Follow these guidelines for including DOIs and URLs in references:

  • Include a DOI for all works that have a DOI, regardless of whether you used the online version or the print version.
  • If a print work does not have a DOI, do not include any DOI or URL in the reference.
  • If an online work has both a DOI and a URL, include only the DOI.
  • For works without DOIs from websites (not including academic research databases), provide a URL in the reference (as long as the URL will work for readers).
  • For works without DOIs from most  academic research databases , do not include a URL or database information in the reference because these works are widely available. The reference should be the same as the reference for a print version of the work.
  • For works from databases that publish original, proprietary material available only in that database (such as the UpToDate database) or for works of limited circulation in databases (such as monographs in the ERIC database), include the name of the database or archive and the URL of the work. If the URL requires a login or is session-specific (meaning it will not resolve for readers), provide the URL of the database or archive home page or login page instead of the URL for the work. See the page on including  database information in references  for more information. 
  • If the URL is no longer working or no longer provides readers access to the content you intend to cite, follow the guidance for works with  no source .
  • Other alphanumeric identifiers such as the International Standard Book Number (ISBN) and the International Standard Serial Number (ISSN) are not included in APA Style references.

Follow these guidelines to format DOIs and URLs:

  • Present both DOIs and URLs as hyperlinks (i.e., beginning with “http:” or “https:”).
  • Because a hyperlink leads readers directly to the content, it is not necessary to include the words “Retrieved from” or “Accessed from” before a DOI or URL.
  • It is acceptable to use either the default display settings for hyperlinks in your word-processing program (e.g., usually blue font, underlined) or plain text that is not underlined.
  • Leave links live if the work is to be published or read online.
  • Follow the current recommendations of the International DOI Foundation to format DOIs in the reference list, which as of this publication is as follows:

https://doi.org/ xxxxx

  • The string “https://doi.org/” is a way of presenting a DOI as a link, and “xxxxx” refers to the DOI number.
  • The preferred format of the DOI has changed over time. Although older works use previous formats (e.g., “http:/dx.doi.org/” or “doi:” or “DOI:” before the DOI number), in your reference list, standardize DOIs into the current preferred format for all entries. For example, use  https://doi.org/10.1037/a0040251  in your reference even though that article, published in 2016, presented the number in an older format.
  • Copy and paste the DOI or URL from your web browser directly into your reference list to avoid transcription errors. Do not change the capitalization or punctuation of the DOI or URL. Do not add line breaks manually to the hyperlink; it is acceptable if your word-processing program automatically adds a break or moves the hyperlink to its own line.
  • Do not add a period after the DOI or URL because this may interfere with link functionality.

When a DOI or URL is long or complex, you may use shortDOIs or shortened URLs if desired.

  • Use the  shortDOI service  provided by the International DOI Foundation to create shortDOIs. A work can have only one DOI and only one shortDOI; the shortDOI service will either produce a new shortDOI for a work that has never had one or retrieve an existing shortDOI.
  • Some websites provide their own branded shortened URLs, and independent URL shortening services are available as well. Any shortened URL is acceptable in a reference as long as you check the link to ensure that it takes you to the correct location.
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Significance and implications of accurate and proper citations in clinical research studies

Citations are an essential component of clinical research studies. In health sciences most articles will refer to over 20 other peer-reviewed publications [ 1 ]. Citations are a core part of the entire research process. Citations fuel literature reviews [ 2 , 3 ] and they allow researchers to link their experiments to previous results and conclusions and establish credibility [ 2 , 4 , 5 ]. Citations can help authors contribute to the growing compilation of literature and prevent plagiarism [ 6 , 7 ]. However, prior studies have acknowledged a prevalence of improper citation [ [8] , [9] , [10] , [11] ]. Studies report citation inaccuracy rates of approximately 20–26% in biomedical literature [ 8 , 9 ]. Some studies have also reported citation inaccuracies within field-specific journals such as pediatric orthopaedics [ 8 ], neurosurgery [ 12 ], spine surgery [ 13 ], and foot and ankle surgery [ 14 ]. This trend is especially alarming as citation inaccuracies can diminish research validity [ 15 ]. Recognizing the causes or instances of inaccurate citations can prevent further improper citation [ 16 ].

1. What are the root causes of citation inaccuracies?

Citation misuse can originate in literature reviews, as authors can find and choose references in arbitrary fashions. This can stem from keyword choice; many authors use broad keywords to garner a large audience, but this can hurt the number of references they receive [ 17 ]. Language can also be a barrier: one study found over 30% of systematic reviews excluded studies not published in English, which dramatically decreases the scope of literature reviews [ 18 ]. Researchers may also be biased towards articles with many citations. This can be described as the ‘Matthew effect:’ the more a paper is referenced, the more it will continue to be referenced [ 19 , 20 ]. This is concerning as citation rate of articles is not necessarily an indicator of quality or significance [ 21 ]. While papers with many citations continue to receive attention, less cited articles may be neglected, potentially hindering research advancements.

Literature reviews may also be influenced by other arbitrary factors. For example, an author's social media presence showed a positive correlation with the rate at which they were cited [ 22 , 23 ]. Another consideration for citation rate is the primacy effect, which describes how citations listed earlier in a study are used more frequently than those that appear toward the end of a study [ 24 ]. The reputation of the author(s), organization(s), journal, or country represented by a paper may also play a role in the number of times it is cited [ 25 ]. Some authors or groups of authors may receive an increased number of citations based on their production level or experience in the field of study [ 25 ]. Additionally, luck and last name may inevitably affect the rate at which someone is repeatedly cited.

2. What are examples of citation inaccuracies?

Selective citation, whether purposeful or subconscious, is an endemic problem [ 11 , 26 , 27 ]. Studies showing positive results are cited more often than those with neutral or negative results, a phenomenon known as citation bias [ 26 ]. This gives readers a biased view and overrepresents positive findings [ 26 ]. Other common forms of improper citation usage include: secondary citation, incorrect/opposite conclusion, back door invention, fact not found, and inaccurate population. Secondary citation, or “amplification,” is the act of citing a fact in a paper that was itself supported by a citation instead of going to the original article [ 16 ]. Amplification leads to the expansion of a belief without additional primary data [ 10 ]. Incorrect/opposite conclusion occurs when inaccurate or missing information is cited. Specifically, an author may cite an article presenting the opposite conclusion referred to in the study [ 16 ]. This error is especially detrimental as studies make claims contradicting the citation, yet this contradiction may be further perpetuated in future studies via amplification. “Back door invention” is the error of citing abstracts while leading the reader to believe it is a peer-reviewed article [ 10 ]. Fact not found consists of a claim that a cited article has stated a fact or statistic, when in reality did not mention it at all and is therefore unsupported [ 16 ]. Lastly, inaccurate population involves the referencing of a study which may have found the results reported, but the results obtained in the cited article may not be generalizable to the population in the new study [ 16 ]. Research has also shown that citation of retracted studies occurs in many fields and these studies are often cited positively [ [28] , [29] , [30] , [31] ]. One study showed that even after 5 years, retracted studies by an author were still being cited, with only 25% of citations acknowledging it had been retracted [ 31 ].

3. What can be done to prevent or correct citation inaccuracies?

Solutions to many of these problems have been shared [ [15] , [16] , [17] , 22 , 23 ]. Authors can help others find their research by using targeted rather than generic keywords [ 17 ]. Similarly, a social media presence by journals and authors may be warranted to improve discoverability [ 22 , 23 ]. While not feasible for all literature reviews, machine learning has been used in finding relevant references for systematic reviews [ 32 ]. In short, machine learning is a form of artificial intelligence that allows systems to create algorithms based on data received. Future improvements in machine learning may allow for widespread use in finding and citing references in a way that is both efficient and accurate. One solution that has been proposed is the development of a tool named MyCites [ 33 ]. This tool would allow for the ability to mark citations as inaccurate and have these notations travel with the digital document so that future readers are aware of the accuracy of any contested citations [ 33 ]. These capabilities may help to stifle early citation inaccuracies and prevent the amplification of inaccurate citations.

Given the prevalence of citation inaccuracies, it is imperative those involved in the peer review process review submissions with an eye toward citation accuracy. At the start, authors must thoroughly recheck their citations and verify the relevance and validity of each reference. [ 34 ] One survey showed that only 4% of published scientists regularly check citations in articles they read [ 3 ]. Some authors have suggested that a simple checklist would avoid most errors [ 16 ]. It has also been suggested that editors develop training courses for authors outlining the acceptable citation styles pertinent to a particular journal [ 34 ]. Reviewers are in the unique role of making sure that new submissions are, evidence-based, in publishable condition, and add to the current body of knowledge. Such responsibility also includes evaluating the references of these submissions and suggesting the alteration, removal, or addition of references which would ensure citation accuracy [ 34 ]. The peer review process can help correct citation mistakes, especially through increased spot checks by editors/reviewers [ 9 ]. Lastly, the publisher's role in citation accuracy has started to include the use of software to process, link, and check the quality of references. [ 35 ] The increased utilization of new technology to verify citation accuracy will be of great benefit to both researchers and readers.

We also seek to share common guidelines for proper citation. First, ensure the citation provides correct publication details, including name, article title, and journal [ 15 ]. Second, the citation must substantiate the claim [ 15 ]. Next, authors should use unbiased sources that provide reliable data [ 15 ]. Articles from prestigious journals should not be assumed as reliable; analysis of the article itself is critical [ 15 ]. Additionally, be mindful of reconciling evidence. Authors should present the information in an objective manner [ 15 ]. In research it is crucial for “evidence to guide conclusions.” [ 36 ] Citations are an important part of the scientific process. They allow researchers to support and share findings, helping to further innovation. However, citations can be misused, slowing progress in clinical research and circulating unsupported beliefs. Many problems with citations can be fixed with increased attention to detail by authors and editors, ultimately strengthening credibility of the literature.

Ethical approval

Not applicable.

Sources of funding

Author contribution.

Study design and conception: AE. Data collection, interpretation and analysis: MN, CA, AE. Manuscript preparation: MN, CA, AE, MM. Critical revision of manuscript: MN, CA, MM, AE. All authors read and approved the final manuscript.

Trial registry number

  • 1. Name of the registry:
  • 2. Unique Identifying number or registration ID:
  • 3. Hyperlink to the registration (must be publicly accessible):

Adel Elkbuli.

Mark McKenney

Declaration of competing interest

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Citation Analysis

What is citation analysis?

Citation analysis is a way of measuring the relative importance or impact of an author, an article or a publication by counting the number of times that author, article, or publication has been cited by other works.

Why conduct citation analysis?

Citation analysis may be conducted for following purposes:

  • To establish the impact that a particular work has had by identifying which other authors based their work upon it or cited it within their own papers.
  • To learn more about a field or a topic by identifying seminal works in that area.
  • To determine what impact a particular author has had within his/her own discipline and beyond by looking at his/her total number of citations broken down by discipline and by country.
  • For promotion and tenure purposes by looking at the quality of sources where a scholar’s work has been published and cited

Sources for Citation Analysis: There are several tools available for citation analysis, some are subscription-based and others are free. Each tool has its strengths and weaknesses and none of them covers the entire universe of scholarly publications. Therefore, it is important to use more than one tool to get a fuller picture of the scholarly impact of an author or a journal. Below is a table highlighting the characteristics of three major citation analysis tools:

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  • Vancouver Referencing | A Quick Guide & Reference Examples

Vancouver Referencing | A Quick Guide & Reference Examples

Published on 18 February 2020 by Jack Caulfield . Revised on 19 August 2022.

Vancouver is a system of referencing commonly used in biomedicine, among other scientific disciplines. In Vancouver style, you place a reference number in the text wherever a source is cited:

This number corresponds to an entry in your reference list – a numbered list of all the sources cited in your text, giving complete information on each:

This quick guide presents the most common rules for Vancouver style referencing. Note that some universities and journals have their own guidelines for the formatting of Vancouver references.

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Table of contents

Vancouver in-text citations, creating a vancouver reference list, vancouver reference examples, missing information in vancouver references, frequently asked questions about vancouver referencing.

In Vancouver style, citations are marked in your text with numbers. These numbers appear either in parentheses or in superscript – choose one option and stick to it consistently:

The numbers usually appear after the name of the author or after a direct quote. They may also appear at the end of the sentence:

Naming authors

You will often need to mention the author when referring to a work or introducing a quote. Only use the author’s last name in your text. If a source has multiple authors, name only the first author followed by ‘et al.’:

It’s not always necessary to mention the author’s name in your text – but always include the reference number when you refer to a source:

Numbering references

Sources are numbered based on the order in which they are cited in the text: the first source you cite is 1, the second 2, and so on.

If the same source is cited again, use the same number to refer to it throughout your paper. This means that the numbers might not appear in consecutive order in your text:

Citing multiple sources

You can also cite multiple sources in the same place:

To cite several sources that appear consecutively in your numbered list, you can use an en dash to mark the range.

In this case, the citation refers the reader to sources 1, 4, 5, 6, and 7.

Citing page numbers

You must specify a page number or range when you directly quote a text, and it can be helpful to do so when you are paraphrasing a particular passage.

Place the page number after the reference number inside the same parentheses, preceded by ‘p.’:

If you’re using superscript numbers, the page number also appears in superscript, in parentheses after the reference number:

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Your reference list is where you provide the information your readers will need in order to look up the sources cited in your text. It consists of a numbered list of all your sources, providing key information including the author, title and publication date of each source.

The list appears in numerical order at the end of your paper. Each entry ends with a full stop, unless the last element is a DOI or URL.

Vancouver reference list example

Vancouver reference list example

Author names

Each entry starts with the author’s last name and initials.

When a source has more than one author, their names are separated by commas. If a source has more than six authors, list the first six followed by ‘et al.’

Source titles

Only the first word of the title and subtitle, along with any proper nouns, are capitalised:

Titles in Vancouver referencing are consistently written in plain text. Do not use italics or quotation marks.

The information you provide differs according to the type of source you’re citing, since different details are relevant in different cases. Formats and examples for the most commonly cited source types are given below.

  • Book chapter
  • Journal article

Some sources will be missing some of the information needed for a complete reference. See below for how to handle missing elements.

As shown in the website example above, when no individual author is named, you can usually name the organisation that produced the source as the author.

If there is no clear corporate author – for example, a wiki that is created and updated collaboratively by users – you can begin your reference with the title instead:

Sources such as websites may lack a clear publication date. In these cases you can omit the year in your reference and just include the date of your citation:

No page numbers

You may want to show the location of a direct quote from a source without page numbers, such as a website. When the source is short, you can often just omit this, but where you feel it’s necessary you can use an alternate locator like a heading or paragraph number:

Harvard referencing uses an author–date system. Sources are cited by the author’s last name and the publication year in brackets. Each Harvard in-text citation corresponds to an entry in the alphabetised reference list at the end of the paper.

Vancouver referencing uses a numerical system. Sources are cited by a number in parentheses or superscript. Each number corresponds to a full reference at the end of the paper.

A citation should appear wherever you use information or ideas from a source, whether by quoting or paraphrasing its content.

In Vancouver style , you have some flexibility about where the citation number appears in the sentence – usually directly after mentioning the author’s name is best, but simply placing it at the end of the sentence is an acceptable alternative, as long as it’s clear what it relates to.

In Vancouver style , when you refer to a source with multiple authors in your text, you should only name the first author followed by ‘et al.’. This applies even when there are only two authors.

In your reference list, include up to six authors. For sources with seven or more authors, list the first six followed by ‘et al.’.

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Caulfield, J. (2022, August 19). Vancouver Referencing | A Quick Guide & Reference Examples. Scribbr. Retrieved 8 April 2024, from https://www.scribbr.co.uk/referencing/vancouver-style/

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MLA In-Text Citations: The Basics

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MLA (Modern Language Association) style is most commonly used to write papers and cite sources within the liberal arts and humanities. This resource, updated to reflect the MLA Handbook (9 th ed.), offers examples for the general format of MLA research papers, in-text citations, endnotes/footnotes, and the Works Cited page.

Guidelines for referring to the works of others in your text using MLA style are covered throughout the  MLA Handbook  and in chapter 7 of the  MLA Style Manual . Both books provide extensive examples, so it's a good idea to consult them if you want to become even more familiar with MLA guidelines or if you have a particular reference question.

Basic in-text citation rules

In MLA Style, referring to the works of others in your text is done using parenthetical citations . This method involves providing relevant source information in parentheses whenever a sentence uses a quotation or paraphrase. Usually, the simplest way to do this is to put all of the source information in parentheses at the end of the sentence (i.e., just before the period). However, as the examples below will illustrate, there are situations where it makes sense to put the parenthetical elsewhere in the sentence, or even to leave information out.

General Guidelines

  • The source information required in a parenthetical citation depends (1) upon the source medium (e.g. print, web, DVD) and (2) upon the source’s entry on the Works Cited page.
  • Any source information that you provide in-text must correspond to the source information on the Works Cited page. More specifically, whatever signal word or phrase you provide to your readers in the text must be the first thing that appears on the left-hand margin of the corresponding entry on the Works Cited page.

In-text citations: Author-page style

MLA format follows the author-page method of in-text citation. This means that the author's last name and the page number(s) from which the quotation or paraphrase is taken must appear in the text, and a complete reference should appear on your Works Cited page. The author's name may appear either in the sentence itself or in parentheses following the quotation or paraphrase, but the page number(s) should always appear in the parentheses, not in the text of your sentence. For example:

Both citations in the examples above, (263) and (Wordsworth 263), tell readers that the information in the sentence can be located on page 263 of a work by an author named Wordsworth. If readers want more information about this source, they can turn to the Works Cited page, where, under the name of Wordsworth, they would find the following information:

Wordsworth, William. Lyrical Ballads . Oxford UP, 1967.

In-text citations for print sources with known author

For print sources like books, magazines, scholarly journal articles, and newspapers, provide a signal word or phrase (usually the author’s last name) and a page number. If you provide the signal word/phrase in the sentence, you do not need to include it in the parenthetical citation.

These examples must correspond to an entry that begins with Burke, which will be the first thing that appears on the left-hand margin of an entry on the Works Cited page:

Burke, Kenneth. Language as Symbolic Action: Essays on Life, Literature, and Method . University of California Press, 1966.

In-text citations for print sources by a corporate author

When a source has a corporate author, it is acceptable to use the name of the corporation followed by the page number for the in-text citation. You should also use abbreviations (e.g., nat'l for national) where appropriate, so as to avoid interrupting the flow of reading with overly long parenthetical citations.

In-text citations for sources with non-standard labeling systems

If a source uses a labeling or numbering system other than page numbers, such as a script or poetry, precede the citation with said label. When citing a poem, for instance, the parenthetical would begin with the word “line”, and then the line number or range. For example, the examination of William Blake’s poem “The Tyger” would be cited as such:

The speaker makes an ardent call for the exploration of the connection between the violence of nature and the divinity of creation. “In what distant deeps or skies. / Burnt the fire of thine eyes," they ask in reference to the tiger as they attempt to reconcile their intimidation with their relationship to creationism (lines 5-6).

Longer labels, such as chapters (ch.) and scenes (sc.), should be abbreviated.

In-text citations for print sources with no known author

When a source has no known author, use a shortened title of the work instead of an author name, following these guidelines.

Place the title in quotation marks if it's a short work (such as an article) or italicize it if it's a longer work (e.g. plays, books, television shows, entire Web sites) and provide a page number if it is available.

Titles longer than a standard noun phrase should be shortened into a noun phrase by excluding articles. For example, To the Lighthouse would be shortened to Lighthouse .

If the title cannot be easily shortened into a noun phrase, the title should be cut after the first clause, phrase, or punctuation:

In this example, since the reader does not know the author of the article, an abbreviated title appears in the parenthetical citation, and the full title of the article appears first at the left-hand margin of its respective entry on the Works Cited page. Thus, the writer includes the title in quotation marks as the signal phrase in the parenthetical citation in order to lead the reader directly to the source on the Works Cited page. The Works Cited entry appears as follows:

"The Impact of Global Warming in North America." Global Warming: Early Signs . 1999. www.climatehotmap.org/. Accessed 23 Mar. 2009.

If the title of the work begins with a quotation mark, such as a title that refers to another work, that quote or quoted title can be used as the shortened title. The single quotation marks must be included in the parenthetical, rather than the double quotation.

Parenthetical citations and Works Cited pages, used in conjunction, allow readers to know which sources you consulted in writing your essay, so that they can either verify your interpretation of the sources or use them in their own scholarly work.

Author-page citation for classic and literary works with multiple editions

Page numbers are always required, but additional citation information can help literary scholars, who may have a different edition of a classic work, like Marx and Engels's  The Communist Manifesto . In such cases, give the page number of your edition (making sure the edition is listed in your Works Cited page, of course) followed by a semicolon, and then the appropriate abbreviations for volume (vol.), book (bk.), part (pt.), chapter (ch.), section (sec.), or paragraph (par.). For example:

Author-page citation for works in an anthology, periodical, or collection

When you cite a work that appears inside a larger source (for instance, an article in a periodical or an essay in a collection), cite the author of the  internal source (i.e., the article or essay). For example, to cite Albert Einstein's article "A Brief Outline of the Theory of Relativity," which was published in  Nature  in 1921, you might write something like this:

See also our page on documenting periodicals in the Works Cited .

Citing authors with same last names

Sometimes more information is necessary to identify the source from which a quotation is taken. For instance, if two or more authors have the same last name, provide both authors' first initials (or even the authors' full name if different authors share initials) in your citation. For example:

Citing a work by multiple authors

For a source with two authors, list the authors’ last names in the text or in the parenthetical citation:

Corresponding Works Cited entry:

Best, David, and Sharon Marcus. “Surface Reading: An Introduction.” Representations , vol. 108, no. 1, Fall 2009, pp. 1-21. JSTOR, doi:10.1525/rep.2009.108.1.1

For a source with three or more authors, list only the first author’s last name, and replace the additional names with et al.

Franck, Caroline, et al. “Agricultural Subsidies and the American Obesity Epidemic.” American Journal of Preventative Medicine , vol. 45, no. 3, Sept. 2013, pp. 327-333.

Citing multiple works by the same author

If you cite more than one work by an author, include a shortened title for the particular work from which you are quoting to distinguish it from the others. Put short titles of books in italics and short titles of articles in quotation marks.

Citing two articles by the same author :

Citing two books by the same author :

Additionally, if the author's name is not mentioned in the sentence, format your citation with the author's name followed by a comma, followed by a shortened title of the work, and, when appropriate, the page number(s):

Citing multivolume works

If you cite from different volumes of a multivolume work, always include the volume number followed by a colon. Put a space after the colon, then provide the page number(s). (If you only cite from one volume, provide only the page number in parentheses.)

Citing the Bible

In your first parenthetical citation, you want to make clear which Bible you're using (and underline or italicize the title), as each version varies in its translation, followed by book (do not italicize or underline), chapter, and verse. For example:

If future references employ the same edition of the Bible you’re using, list only the book, chapter, and verse in the parenthetical citation:

John of Patmos echoes this passage when describing his vision (Rev. 4.6-8).

Citing indirect sources

Sometimes you may have to use an indirect source. An indirect source is a source cited within another source. For such indirect quotations, use "qtd. in" to indicate the source you actually consulted. For example:

Note that, in most cases, a responsible researcher will attempt to find the original source, rather than citing an indirect source.

Citing transcripts, plays, or screenplays

Sources that take the form of a dialogue involving two or more participants have special guidelines for their quotation and citation. Each line of dialogue should begin with the speaker's name written in all capitals and indented half an inch. A period follows the name (e.g., JAMES.) . After the period, write the dialogue. Each successive line after the first should receive an additional indentation. When another person begins speaking, start a new line with that person's name indented only half an inch. Repeat this pattern each time the speaker changes. You can include stage directions in the quote if they appear in the original source.

Conclude with a parenthetical that explains where to find the excerpt in the source. Usually, the author and title of the source can be given in a signal phrase before quoting the excerpt, so the concluding parenthetical will often just contain location information like page numbers or act/scene indicators.

Here is an example from O'Neill's  The Iceman Cometh.

WILLIE. (Pleadingly) Give me a drink, Rocky. Harry said it was all right. God, I need a drink.

ROCKY. Den grab it. It's right under your nose.

WILLIE. (Avidly) Thanks. (He takes the bottle with both twitching hands and tilts it to his lips and gulps down the whiskey in big swallows.) (1.1)

Citing non-print or sources from the Internet

With more and more scholarly work published on the Internet, you may have to cite sources you found in digital environments. While many sources on the Internet should not be used for scholarly work (reference the OWL's  Evaluating Sources of Information  resource), some Web sources are perfectly acceptable for research. When creating in-text citations for electronic, film, or Internet sources, remember that your citation must reference the source on your Works Cited page.

Sometimes writers are confused with how to craft parenthetical citations for electronic sources because of the absence of page numbers. However, these sorts of entries often do not require a page number in the parenthetical citation. For electronic and Internet sources, follow the following guidelines:

  • Include in the text the first item that appears in the Work Cited entry that corresponds to the citation (e.g. author name, article name, website name, film name).
  • Do not provide paragraph numbers or page numbers based on your Web browser’s print preview function.
  • Unless you must list the Web site name in the signal phrase in order to get the reader to the appropriate entry, do not include URLs in-text. Only provide partial URLs such as when the name of the site includes, for example, a domain name, like  CNN.com  or  Forbes.com,  as opposed to writing out http://www.cnn.com or http://www.forbes.com.

Miscellaneous non-print sources

Two types of non-print sources you may encounter are films and lectures/presentations:

In the two examples above “Herzog” (a film’s director) and “Yates” (a presentor) lead the reader to the first item in each citation’s respective entry on the Works Cited page:

Herzog, Werner, dir. Fitzcarraldo . Perf. Klaus Kinski. Filmverlag der Autoren, 1982.

Yates, Jane. "Invention in Rhetoric and Composition." Gaps Addressed: Future Work in Rhetoric and Composition, CCCC, Palmer House Hilton, 2002. Address.

Electronic sources

Electronic sources may include web pages and online news or magazine articles:

In the first example (an online magazine article), the writer has chosen not to include the author name in-text; however, two entries from the same author appear in the Works Cited. Thus, the writer includes both the author’s last name and the article title in the parenthetical citation in order to lead the reader to the appropriate entry on the Works Cited page (see below).

In the second example (a web page), a parenthetical citation is not necessary because the page does not list an author, and the title of the article, “MLA Formatting and Style Guide,” is used as a signal phrase within the sentence. If the title of the article was not named in the sentence, an abbreviated version would appear in a parenthetical citation at the end of the sentence. Both corresponding Works Cited entries are as follows:

Taylor, Rumsey. "Fitzcarraldo." Slant , 13 Jun. 2003, www.slantmagazine.com/film/review/fitzcarraldo/. Accessed 29 Sep. 2009. 

"MLA Formatting and Style Guide." The Purdue OWL , 2 Aug. 2016, owl.english.purdue.edu/owl/resource/747/01/. Accessed 2 April 2018.

Multiple citations

To cite multiple sources in the same parenthetical reference, separate the citations by a semi-colon:

Time-based media sources

When creating in-text citations for media that has a runtime, such as a movie or podcast, include the range of hours, minutes and seconds you plan to reference. For example: (00:02:15-00:02:35).

When a citation is not needed

Common sense and ethics should determine your need for documenting sources. You do not need to give sources for familiar proverbs, well-known quotations, or common knowledge (For example, it is expected that U.S. citizens know that George Washington was the first President.). Remember that citing sources is a rhetorical task, and, as such, can vary based on your audience. If you’re writing for an expert audience of a scholarly journal, for example, you may need to deal with expectations of what constitutes “common knowledge” that differ from common norms.

Other Sources

The MLA Handbook describes how to cite many different kinds of authors and content creators. However, you may occasionally encounter a source or author category that the handbook does not describe, making the best way to proceed can be unclear.

In these cases, it's typically acceptable to apply the general principles of MLA citation to the new kind of source in a way that's consistent and sensible. A good way to do this is to simply use the standard MLA directions for a type of source that resembles the source you want to cite.

You may also want to investigate whether a third-party organization has provided directions for how to cite this kind of source. For example, Norquest College provides guidelines for citing Indigenous Elders and Knowledge Keepers⁠ —an author category that does not appear in the MLA Handbook . In cases like this, however, it's a good idea to ask your instructor or supervisor whether using third-party citation guidelines might present problems.

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Writing and Citation Resources

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Confused about a writing term and want the definition? This is the place to look! Here you'll find our collection of common terminology associated with the writing process. Choose from the alphabetical listing below to get started, or scroll down the page.

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Is your term not listed here? Send an email to the library at [email protected] and we'll add it to the list!

A detailed examination of a work in order to promote further discussion or provide an interpretation of its meaning.

Annotated Bibliography

An Annotated Bibliography is a list of the resources that you find during the research process. It includes a full citation of each resource and 1-2 paragraphs beneath the citation which summarize the source and its usefulness to your current project. An Annotated Bibliography can include sources you intend to use and sources you have investigated but do not intend to use for your assignment. In that way, an Annotated Bibliography is an organizational tool for longer research projects that helps you to maintain a running list of items you've found.

  • Creating an Annotated Bibliography (APA) Resources to help you write an Annotated Bibliography in APA Style.
  • Creating an Annotated Bibliography (MLA) Resources to help you write an Annotated Bibliography in MLA Style.

An annotation is an explanation or description of an item. In an Annotated Bibliography, the annotation summarizes the work and briefly discusses its application to your research.

  • Sample Annotations

APA style is a format for writing documents created by the American Psychological Association.

Attribution

An attribution mentions the name of the author/owner of a resource. Attributions are a great way to properly transition quoted material into a paper without breaking up the flow of the writing.

Example: As Mr. Smith (2001) states, "there is no need to state the obvious."

In academic writing, the audience is the general reader who may be completely unfamiliar with your topic.

Bibliography

A bibliography is a list of resources used in a project. Typically the bibliography is formatted according to the type of style required (APA, MLA, etc.).

Block Quote

If a direct quote is more than 4 types lines of text, it should be formatted in block quote style. The entire quote is indented one half inch from the left margin, and quotation marks are removed.

  • Example Block Quotes (PDF) This link includes several examples of block quotes in APA style.

Body Paragraphs

The body of the essay consists of every paragraph between the introduction and conclusion paragraph.

Citation/Cite

The act of giving credit to someone for his/her words and ideas, typically done in a predetermined style (APA, MLA, etc.).

Concept Map

A prewriting technique that uses a series of connected bubbles in order to show the relationship of concepts. May also be referred to as webbing and/or brainstorming.

  • Concept Mapping Definitions and Examples This site offers examples for some of the visual techniques used in writing and project planning.

The conclusion paragraph is the final paragraph of an essay. It summarizes the main ideas, re-emphasizes the thesis, and draws the essay to a close.

  • Strategies for Writing a Conclusion This link provides examples of effective conclusions and techniques for writing an effective conclusion paragraph.

Copyright indicates someone's ownership of his/her intellectual property.

Direct Quote

Direct quotes are taken from a resource exactly as they appear in the resource. They are marked in quotation marks to show that they are direct quotes, and must always be cited.

Example: According to Dr. Smith, "direct quotes should always be cited" (142).

Documentation

Documentation provides direct evidence in support of ideas and includes proper citation for source material.

A draft is an unpolished version of a work. In academic writing, a paper can go through many draft versions as revisions take place.

  • Drafting Library guide discussing tips for essay construction.

An endnote is additional information added at the end of a chapter or book. It is typically a reference, explanation, or additional comment on something within the text.

  • Insert or Create Footnotes and Endnotes in Microsoft Word Microsoft Support Center information for creating footnotes and endnotes in your documents.

Formal Outline

A formal outline uses a combination of Roman Numerals (I, II, III, IV; i, ii, iii, iv), letters (A, B, C; a, b, c), and numbers (1, 2, 3) to show the relationship between main points and sub-points in each paragraph of an essay.

  • Formal Outlines Library guide with information and examples for formal outlines.

Free Writing

Free writing is a prewriting technique in which you either write or type your thoughts non-stop and disregard issues with spelling, grammar, or style.

A footnote is placed at the end of a page and provides additional information or a reference for content on that specific page of your document.

Genre is the category into which a work belongs. Popular literary genres include romance, science fiction, and horror. Academic genres include narrative essays, argument essays, compare/contrast essays, and many other variations.

Hanging Indent

Citations are formatted with a hanging indent. The first line of a citation is always aligned with the left margin. If a citation is more than one line in length, every line under the first line is indented by one half inch.

  • Create a Hanging Indent in Microsoft Word Written tutorial to help you easily format your citations with a hanging indent using the rulers in Microsoft Word.

Informal Outline

An informal outline uses bullet points or numbering to show the relationship between main points and sub-points in each paragraph of an essay.

  • Informal Outlines Library guide with information and examples for creating informal outlines.

In-text Citation

An in-text citation, also known as parenthetical citation, is an abbreviated form of a citation found within the body of your paper to show the connection between information presented there and the sources from which you obtained that information. The format of an in-text citation varies depending upon the style that you are using to format the paper.

  • In-Text Citations (APA) Instructions and examples for in-text citations in APA style.
  • In-Text Citations (MLA) Instructions and examples for formatting citations in MLA style.

Introduction

The introduction of an essay provides readers with a broad overview of the topic and typically ends with a thesis statement.

  • How to Write a Strong Introduction Tips for writing a strong introduction paragraph.

Jargon is language used to describe something within a specific field. Experts within the field likely know the meaning of these terms, while those not associated with the field will likely require further explanation in order to interpret their meaning.

MLA style is a format for writing documents created by the Modern Language Association.

  • Purdue OWL: MLA Provides MLA formatting Assistance.

A personal story.

The act of taking notes.

  • Taking Notes that Work Advice for note-taking.

An outline is a list of the concepts within your essay generated before you move them into fully developed paragraphs. Outlines can be either formal or informal, and can be a great organizational tool to help you merge your own ideas with your research before you begin drafting an essay.

Using someone else's words or ideas, but expressing them in different words. Even though the words are not the same, paraphrased material must always be cited.

  • Paraphrasing Techniques Techniques for re-phrasing information in your own words (paraphrasing), including examples.

Parenthetical Citation

An parenthetical citation, also known as in-text citation, is an abbreviated form of a citation found within the body of your paper to show the connection between information presented there and the sources from which you obtained that information. The format of an in-text/parenthetical citation varies depending upon the style that you are using to format the paper.

  • Parenthetical Citations (APA) Instructions and examples for in-text citations in APA style.
  • Parenthetical Citations (MLA) Instructions and examples for formatting citations in MLA style.

Patch Writing

A common error when trying to paraphrase. Rather than completely re-phrasing to capture ideas, pieces of sentences and/or phrases are used from the original source but sometimes placed in a different order. The end result is usually direct quotes from source material that are not formatted in quotation marks.

Peer Reviewed

Peer reviewed resources are materials checked by other scholars in the field for quality and accuracy before publication. They may also be referred to as scholarly or refereed materials.

  • Is Your Source "Scholarly" Enough? Discussion of scholarly publications.

The act of taking someone else's words or ideas and presenting them as your own. Plagiarism can be avoided by giving authors, creators, and/or owners full credit for those words/ideas through citation. Plagiarism can carry heavy penalties in the academic world. In life, plagiarism can be considered copyright infringement.

  • Plagiarism.org Plagiarism.org is a free resource sponsored by iParadigms LLC, makers of Turnitin, WriteCheck, and iThenticate. -- From web site

Point of View

The point of view, or POV, is the perspective from which a story or essay is written. There are three broad levels of point of view: first person, second person, and third person.

First person POV is the least formal perspective, and uses the pronouns I, me, my, we, us, and our to show a personal connection with the subject. It is often used in writing narratives.

Second person POV is used when you are speaking directly to your reader. Most textbooks and instructional manuals are written in second person POV because they are providing instructions to the reader. In second person POV, the pronouns you and your are used.

Third person POV is the most formal point of view, and is used in academic writing. It uses the formal pronouns he/she, him/her, his/her, it, and they.

Prewriting is often the first stage of the writing process. When you prewrite, you generate ideas that you could later develop into an essay or research project. There are many ways to prewrite, including concept mapping, free writing, and outlining.

  • Three Prewriting Strategies for Any Writing Project Provides an overview of prewriting techniques.

Primary Source

A primary source provides original research or information from the era in which it covers. It was written and/or published during that specific time period. The Declaration of Independence is an example of a primary document.

A group of words taken directly from a resource.

Refereed resources are materials checked by other scholars in the field for quality and accuracy before publication. They may also be referred to as scholarly or peer reviewed materials.

References Page

In APA style, the References page is the list of full citations for resources used in your paper. It is located on a separate page at the end of your document.

  • References List: Basic Rules References list formatting in APA style.

Referencing

Referencing is another word for citing. It is giving others credit for their words and/or ideas.

Scholarly resources are materials checked by other scholars in the field for quality and accuracy before publication. They may also be referred to as peer reviewed or refereed materials.

Secondary Source

Secondary sources provide further analysis of a topic or era often by using primary source material.

In academic writing, style is the manner in which something is written or cited. Your writing style, including tone and point of view, can change depending on the type of assignment. Citation style varies by academic discipline.

A summary recounts the main points of a work without providing further analysis.

Theme is the subject matter of a work. In literature, the theme is the underlying meaning of the work.

  • Identifying Themes and Literary Analysis Techniques to extract theme from literary works.

Thesis Statement

The thesis statement, which is usually the last sentence in your introduction paragraph, provides readers with a strong argument for your paper. Every paragraph in the remainder of the essay should then support some aspect of your thesis.

  • Tips and Examples for Writing Thesis Statements Thesis statement examples and tips for constructing an effective thesis statement for various types of assignments.

The tone is the attitude or mood with which a piece of writing is constructed. The tone can be argumentative, informal, emotional, amused, sarcastic, formal, etc. The type of tone used depends largely on the expectations for the assignment.

Topic Sentence

The topic sentence is the first sentence of a paragraph and provides the main idea covered within that paragraph.

Transitions

In writing, transitional words and phrases help to create flow by moving the reader from one topic to the next. This helps paragraphs to read less like a list of ideas and more like a cohesive piece of writing.

  • Transitional Words and Phrases List and definitions of common transitional words and phrases used to create cohesion in an academic essay.

In academic writing, voice is considered the tone and point-of-view within your writing. It is the perspective from which a work is written.

Works Cited Page

In MLA style, the Works Cited page is the list of full citations for resources used in your paper. It is located on a separate page at the end of your document.

  • MLA Works Cited Page: Basic Format Works Cited list formatting in MLA style.
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What is a DOI? | Finding and Using Digital Object Identifiers

Published on December 19, 2018 by Courtney Gahan . Revised on February 24, 2023 by Raimo Streefkerk.

A DOI (Digital Object Identifier) is a unique and never-changing string assigned to online (journal) articles , books , and other works. DOIs make it easier to retrieve works, which is why citation styles, like APA and MLA Style , recommend including them in citations.

You may find DOIs formatted in various ways:

  • doi:10.1080/02626667.2018.1560449
  • https://doi.org/10.1111/hex.12487
  • https://dx.doi.org/10.1080/02626667.2018.1560449
  • https://doi.org/10.1016/j.jpsychires.2017.11.014

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Table of contents

How to find a doi, apa style guidelines for using dois, mla style guidelines for using dois, chicago style guidelines for using dois, frequently asked questions about dois.

The DOI will usually be clearly visible when you open a journal article on a database.

Examples of where to find DOIs

  • Taylor and Francis Online
  • SAGE journals

Taylor and Francis Online DOI

Note: JSTOR uses a different format, but their “stable URL” functions in the same way as a DOI.

What to do when you cannot find the DOI

If you cannot find the DOI for a journal article, you can also check Crossref . Simply paste the relevant information into the “Search Metadata” box to find the DOI. If the DOI does not exist here, the article most likely does not have one; in this case, use a URL instead.

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APA Style guidelines state that DOIs should be included whenever they’re available. In practice, almost all journal articles and most academic books have a DOI assigned to them.

You can find the DOI on the first page of the article or copyright page of a book. Omit the DOI from the APA citation if you cannot find it.

Formatting DOIs in APA Style

DOIs are included at the end of the APA reference entry . In the 6th edition of the APA publication manual, DOIs can be preceded by the label “doi:” or formatted as URLs. In the 7th edition , DOIs should be formatted as URLs with ‘https://doi.org/’ preceding the DOI.

  • APA 6th edition: doi: 10.1177/0269881118806297 or https://doi.org/ 10.1177/0269881118806297
  • APA 7th edition: https://doi.org/ 10.1177/0269881118806297

APA citation examples with DOI

  • Fardouly, J., & Vartanian, L. R. (2016). Social media and body image concerns: Current research and future directions. Current Opinion in Psychology , 9 , 1–5. https://doi.org/10.1016/j.copsyc.2015.09.005
  • Sustersic, M., Gauchet, A., Foote, A., & Bosson, J.-L. (2016). How best to use and evaluate Patient Information Leaflets given during a consultation: a systematic review of literature reviews. Health Expectations , 20 (4), 531–542. https://doi.org/10.1111/hex.12487

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MLA recommends using the format doi:10.1177/0269881118806297.

Generate accurate MLA citations with Scribbr

In Chicago style , the format https://doi.org/10.1177/0269881118806297 is preferred.

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The AI-powered Citation Checker helps you avoid common mistakes such as:

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meaning of research citation

A DOI is a unique identifier for a digital document. DOIs are important in academic citation because they are more permanent than URLs, ensuring that your reader can reliably locate the source.

Journal articles and ebooks can often be found on multiple different websites and databases. The URL of the page where an article is hosted can be changed or removed over time, but a DOI is linked to the specific document and never changes.

The DOI is usually clearly visible when you open a journal article on an academic database. It is often listed near the publication date, and includes “doi.org” or “DOI:”. If the database has a “cite this article” button, this should also produce a citation with the DOI included.

If you can’t find the DOI, you can search on Crossref using information like the author, the article title, and the journal name.

Include the DOI at the very end of the APA reference entry . If you’re using the 6th edition APA guidelines, the DOI is preceded by the label “doi:”. In the 7th edition , the DOI is preceded by ‘https://doi.org/’.

  • 6th edition: doi: 10.1177/0894439316660340
  • 7th edition: https://doi.org/ 10.1177/0894439316660340

APA citation example (7th edition)

Hawi, N. S., & Samaha, M. (2016). The relations among social media addiction, self-esteem, and life satisfaction in university students. Social Science Computer Review , 35 (5), 576–586. https://doi.org/10.1177/0894439316660340

In an APA journal citation , if a DOI (digital object identifier) is available for an article, always include it.

If an article has no DOI, and you accessed it through a database or in print, just omit the DOI.

If an article has no DOI, and you accessed it through a website other than a database (for example, the journal’s own website), include a URL linking to the article.

In MLA style citations , format a DOI as a link, including “https://doi.org/” at the start and then the unique numerical code of the article.

DOIs are used mainly when citing journal articles in MLA .

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the “Cite this Scribbr article” button to automatically add the citation to our free Citation Generator.

Gahan, C. (2023, February 24). What is a DOI? | Finding and Using Digital Object Identifiers. Scribbr. Retrieved April 8, 2024, from https://www.scribbr.com/citing-sources/what-is-a-doi/

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eMethods. Adjudication Process

eFigure 1. Proportion of Patients With an Adjudicated Diagnosis of Type 1 Myocardial Infarction and Type 2 Myocardial Infarction Who Had a Clinical Diagnosis of Myocardial Infarction in the Hospital Record Over 6-Month Blocks in Scotland and Sweden

eFigure 2. Cumulative Incidence of Cardiovascular Death or Myocardial Infarction in All Universal Definition Subtypes of Myocardial Infarction With No ST Elevation and ST Elevations Stratified According to Those With a Clinical Diagnosis and Without a Clinical Diagnosis of Myocardial Infarction

eFigure 3. Cumulative Incidence of All Cause Death in All Myocardial Infarctions in Scotland and Sweden Stratified According to Those With a Clinical Diagnosis and Without a Clinical Diagnosis of Myocardial Infarction

eFigure 4. Cumulative Incidence of Death From Any Cause at 1 Year in Patients With an Adjudicated Diagnosis of Type 1 Myocardial Infarction and Adjudicated Diagnosis of Type 2 Myocardial Infarction Stratified According to Those With a Clinical Diagnosis and Without a Clinical Diagnosis of Myocardial Infarction

eFigure 5. Cumulative Incidence of Death From Cardiovascular Causes at 1 Year in Patients With an Adjudicated Diagnosis of Type 1 Myocardial Infarction and Adjudicated Diagnosis of Type 2 Myocardial Infarction Stratified According to Those With a Clinical Diagnosis and Without a Clinical Diagnosis of Myocardial Infarction

eFigure 6. Cumulative Incidence Death From Noncardiovascular Causes at 1 Year in Patients With an Adjudicated Diagnosis of Type 1 Myocardial Infarction and Adjudicated Diagnosis of Type 2 Myocardial Infarction Stratified According to Those With a Clinical Diagnosis and Without a Clinical Diagnosis of Myocardial Infarction

eReferences.

eTable 1. Clinical Characteristics of Cohorts From Scotland and Sweden

eTable 2. Characteristics Associated With a Clinical Diagnosis of Myocardial Infarction Stratified by the Universal Definition

eTable 3. Management and Outcomes of Patients With and Without a Clinical Diagnosis of Myocardial Infarction Stratified by the Universal Definition

eTable 4. Risk of Subsequent Myocardial Infarction or Cardiovascular Death at 1 Year in Patients With a Clinical Diagnosis of Myocardial Infarction Compared to Those Without a Clinical Diagnosis Stratified by the Universal Definition

eTable 5. Clinical Diagnosis of Myocardial Infarction Using Different Positions in the Hospital Record for Patients With an Adjudicated Diagnosis in Scotland

eTable 6. Additional Analysis Stratifying by the Presence of ST-Elevation on the Electrocardiogram and Effect on the Diagnostic Performance of a Clinical Diagnosis of Myocardial Infarction in the Hospital Record Stratified by the Universal Definition

eTable 7. Characteristics Associated With a Clinical Diagnosis in Populations of Both ST Segment Elevation and Non-ST-Elevation Myocardial Infarctions in Scotland

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Taggart C , Roos A , Kadesjö E, et al. Application of the Universal Definition of Myocardial Infarction in Clinical Practice in Scotland and Sweden. JAMA Netw Open. 2024;7(4):e245853. doi:10.1001/jamanetworkopen.2024.5853

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Application of the Universal Definition of Myocardial Infarction in Clinical Practice in Scotland and Sweden

  • 1 British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, United Kingdom
  • 2 Department of Emergency and Reparative Medicine, Karolinska University Hospital, Stockholm, Sweden
  • 3 Department of Medicine, Clinical Epidemiology Division, Karolinska Institutet, Stockholm, Sweden
  • 4 Department of Medicine, Karolinska Institutet, Stockholm, Sweden
  • 5 Department of Non-communicable Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, United Kingdom
  • 6 Department of Cardiology, Uppsala University, Uppsala, Sweden
  • 7 Department of Cardiology, Södersjukhuset, Stockholm, Sweden
  • 8 Usher Institute, University of Edinburgh, Edinburgh, United Kingdom

Question   How is the universal definition of myocardial infarction (MI), which differentiates type 1 (atherothrombosis) from type 2 (oxygen supply-demand imbalance) MI, applied in clinical practice?

Findings   In this cohort study of 50 356 patients, few patients meeting the diagnostic criteria for type 2 MI received a clinical diagnosis of MI in practice, and type 1 MI was underdiagnosed in women and older people.

Meaning   These findings suggest that uncertainty remains regarding the diagnostic criteria or value of the universal definition of MI.

Importance   Whether the diagnostic classifications proposed by the universal definition of myocardial infarction (MI) to identify type 1 MI due to atherothrombosis and type 2 MI due to myocardial oxygen supply-demand imbalance have been applied consistently in clinical practice is unknown.

Objective   To evaluate the application of the universal definition of MI in consecutive patients with possible MI across 2 health care systems.

Design, Setting, and Participants   This cohort study used data from 2 prospective cohorts enrolling consecutive patients with possible MI in Scotland (2013-2016) and Sweden (2011-2014) to assess accuracy of clinical diagnosis of MI recorded in hospital records for patients with an adjudicated diagnosis of type 1 or type 2 MI. Data were analyzed from August 2022 to February 2023.

Main Outcomes and Measures   The main outcome was the proportion of patients with a clinical diagnosis of MI recorded in the hospital records who had type 1 or type 2 MI, adjudicated by an independent panel according to the universal definition. Characteristics and risk of subsequent MI or cardiovascular death at 1 year were compared.

Results   A total of 50 356 patients were assessed. The cohort from Scotland included 28 783 (15 562 men [54%]; mean [SD] age, 60 [17] years), and the cohort from Sweden included 21 573 (11 110 men [51%]; mean [SD] age, 56 [17] years) patients. In Scotland, a clinical diagnosis of MI was recorded in 2506 of 3187 patients with an adjudicated diagnosis of type 1 MI (79%) and 122 of 716 patients with an adjudicated diagnosis of type 2 MI (17%). Similar findings were observed in Sweden, with 970 of 1111 patients with adjudicated diagnosis of type 1 MI (87%) and 57 of 251 patients with adjudicated diagnosis of type 2 MI (23%) receiving a clinical diagnosis of MI. Patients with an adjudicated diagnosis of type 1 MI without a clinical diagnosis were more likely to be women (eg, 336 women [49%] vs 909 women [36%] in Scotland; P  < .001) and older (mean [SD] age, 71 [14] v 67 [14] years in Scotland, P  < .001) and, when adjusting for competing risk from noncardiovascular death, were at similar or increased risk of subsequent MI or cardiovascular death compared with patients with a clinical diagnosis of MI (eg, 29% vs 18% in Scotland; P  < .001).

Conclusions and Relevance   In this cohort study, the universal definition of MI was not consistently applied in clinical practice, with a minority of patients with type 2 MI identified, and type 1 MI underrecognized in women and older persons, suggesting uncertainty remains regarding the diagnostic criteria or value of the classification.

The universal definition of myocardial infarction (UDMI) is endorsed by the World Health Organization and encourages the use of standard criteria for the diagnosis of MI worldwide. 1 - 3 In 2007, a classification into subtypes was introduced that recognized there are different underlying pathophysiological mechanisms of MI. 4 Type 1 MI due to coronary atherothrombosis is well established in practice, and clear guidance is available for management and treatment of this condition. 2 In contrast, type 2 MI due to oxygen supply-demand imbalance may be triggered by multiple conditions, and the implications of this diagnosis in practice are less certain. 5 - 9

Outcomes for patients with type 2 MI are variable and are often worse than for patients with type 1 MI. 10 - 14 Patients with type 2 MI often are older and have more comorbidities, 15 but differences in outcome may also reflect uncertainty in practice and variation in the management of patients with type 2 MI. It is currently unclear whether the diagnostic criteria proposed by the UDMI are consistently applied in clinical practice.

In consecutive patients with possible MI presenting to secondary or tertiary care hospitals across 2 different countries, we evaluated the proportion of patients with a clinical diagnosis of MI recorded in the hospital records who had type 1 and type 2 MI as adjudicated by an independent panel according to the UDMI. We compared the characteristics and outcomes in patients with and without a clinical diagnosis MI.

This cohort study was conducted according to the Declaration of Helsinki and approved by local research ethics committees in Scotland and Sweden. These approvals did not require individual patient consent, as both Scotland and Sweden allow for research to take place without consent in limited circumstance. 16 , 17 All data were linked and deidentified within an approved secure data environment (DataLoch). We adhered to the Strengthening the Reporting of Observational Studies in Epidemiology ( STROBE ) reporting guideline.

For the cohort from Scotland, we used data from High-Sensitivity Troponin in the Evaluation of Patients With Suspected Acute Coronary Syndrome (High-STEACS) trial. 18 High-STEACS evaluated the implementation of a high-sensitivity cardiac troponin I assay in consecutive patients with suspected MI across 10 secondary and tertiary care hospitals in Scotland between 2013 and 2016. Patients were eligible for inclusion if they presented with suspected MI and had paired contemporary and high-sensitivity cardiac troponin measurements. Patients were excluded if they had been admitted previously during the trial period or were not residents of Scotland.

For the cohort from Sweden, we used data from a prospective observational cohort study of patients with suspected MI who attended the emergency department (ED) of Karolinska University Hospital in Stockholm between 2011 and 2014. 19 All patients older than 25 years attending the ED with chest pain in whom at least 1 measurement of high-sensitivity cardiac troponin was available were eligible for inclusion.

For this study, we excluded patients where adjudicators determined there was insufficient clinical information to enable adjudication of diagnosis. This was a result of not having access to linked records describing presentation to ED or hospital admission. For the cohort from Scotland, we also excluded patients admitted during the validation phase of the trial, as care was not guided by a high-sensitivity troponin assay.

All patients with evidence of myocardial injury were adjudicated and classified according to the fourth UDMI (eMethods in Supplement 1 ). In the cohort from Scotland, myocardial injury was defined as any high-sensitivity troponin I concentration above the sex-specific 99th percentile threshold. Cardiac troponin was measured using the ARCHITECT STAT high-sensitive troponin I assay (Abbott Diagnostics), with the 99th percentile defined as 34 ng/L in men and 16 ng/L in women (to convert to nanograms per milliliter, multiply by 0.001). 20 In the cohort from Sweden, myocardial injury was defined as any high-sensitivity cardiac troponin T concentration above the uniform 99th percentile threshold. Cardiac troponin was measured using the Elecsys high-sensitivity troponin T (Roche Diagnostics), with the 99th percentile defined as 14 ng/L. 21

Clinical diagnoses were listed by the consultant overseeing patients care on hospital discharge letter. Letters were reviewed by a team of professional coders at each hospital site who classified clinical diagnoses according to the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision ( ICD-10 ) system. The classification was then reviewed and finalized by Public Health Scotland and the original patient’s consultant to create the Scottish Morbidity Record and Swedish Patient Register. For primary analysis, we identified patients with MI if an I21 or I22 code was listed in the first or any subsequent position.

For the cohort from Scotland, regional and national registries were used to collect data on outcomes, and all subsequent hospital admissions with myocardial injury or deaths were adjudicated by clinicians blinded to the index diagnosis and study phase as previously described. 18 For the cohort from Sweden, the Swedish National Patient Register and Causes of Death Register were used to identify subsequent hospital admissions and cause-specific deaths. For this analysis, the primary outcome was subsequent MI after index hospital presentation ( ICD-10 codes I22-I22) or cardiovascular death at 1 year. Secondary outcomes included subsequent MI, cardiovascular death, or all-cause death at 1 year.

We calculated sensitivity, specificity, negative predictive value, and positive predictive value of clinical diagnosis of MI for any adjudicated diagnosis of MI and for type 1 and type 2 MI separately. The 95% CIs were determined using a bayesian approach by sampling from a binomial likelihood with noninformative Jeffreys prior (both β-distribution shape parameters = 0.5). We used the Cohen κ to evaluate concordance between clinical and adjudicated diagnosis of MI.

In patients with an adjudicated diagnosis of type 1 or type 2 MI, we conducted univariable and multivariable logistic regression analyses to quantify the association between clinical characteristics and the odds of a clinical diagnosis of MI. We adjusted for age, sex, hemoglobin and estimated glomerular filtration rate (eGFR) at presentation, peak cardiac troponin concentrations as well as a previous diagnosis of ischemic heart disease, previous cerebrovascular disease, diabetes, previous heart failure hospitalization, and myocardial ischemia. To achieve a normal distribution, we log 2 transformed cardiac troponin.

We estimated the cumulative incidence of the primary outcome, and group comparisons were made using log-rank test. Cox regression analyses were conducted to evaluate the association between receiving a clinical diagnosis of MI and the primary outcome. In multivariable analyses, we adjusted for age and sex and subsequently added the covariates to the model used in logistic regression analysis. Noncardiovascular death was considered a competing risk.

We conducted several exploratory analyses. We evaluated whether the position of ICD-10 code within the hospital record from the first up to the sixth position influenced agreement with adjudicated diagnosis. Second, we assessed agreement between clinical and adjudicated diagnoses in patients with ST-segment elevation (STEMI) and non-STEMI separately. Finally, we evaluated differences between patients who did and did not receive a clinical diagnosis of MI in association with secondary outcomes.

Multiple imputation by chained equations was used to impute missing covariate data using other clinical characteristics and outcomes. All analyses were undertaken between August 2022 and February 2023 using R software version 3.6.3 (R Project for Statistical Computing). Comparisons with a 2-sided P  < .05 were considered statistically significant.

A total of 50 356 patients were assessed. The cohort from Scotland included 28 783 patients (15 562 men [54%]; mean [SD] age, 60 [17] years), and the cohort from Sweden included 21 573 patients (11 110 men [51%]; mean [SD] age, 56 [17] years) ( Figure 1 ; eTable 1 in Supplement 1 ). In Scotland, 3187 patients (11%) had an adjudicated diagnosis of type 1 MI and 716 patients (3%) had an adjudicated diagnosis of type 2 MI ( Table 1 ). In Sweden, 1111 patients (5%) had an adjudicated diagnosis of type 1 MI and 251 patients (1%) had an adjudicated diagnosis of type 2 MI ( Table 1 ).

A clinical diagnosis of MI was recorded in 2657 of 3941 patients (67%) with any adjudicated MI diagnosis in Scotland (κ = 0.757) and 1027 of 1362 patients (75%) with any adjudicated MI diagnosis in Sweden (κ = 0.839) ( Table 2 ). In Scotland, a clinical diagnosis of MI was recorded in 2506 patients (79%) with an adjudicated type 1 MI diagnosis and 122 patients (17%) with an adjudicated type 2 MI diagnosis ( Figure 2 ). Findings were consistent in the cohort from Sweden, with 970 patients (87%) with a type 1 MI diagnosis and 57 patients (23%) with a type 2 MI diagnosis receiving a clinical diagnosis of MI. A small number of patients received a clinical diagnosis of MI but not an adjudicated diagnosis of any type of MI (Scotland: 169 patients [0.4%]; Sweden: 33 patients [0.2%]). No differences were observed in the proportion of patients receiving a clinical diagnosis of MI over time ( eFigure 1 in Supplement 1 ).

In Scotland, patients with an adjudicated diagnosis of type 1 MI without a clinical diagnosis of MI were more likely to be women (336 patients [49%] vs 909 patients [36%]; P  < .001) and to be older (mean [SD] age, 71 [14] years vs 67 [14] years; P  < .001) than patients who received a clinical diagnosis of MI. In contrast, no differences were observed in the clinical characteristics between patients with an adjudicated diagnosis of type 2 MI with and without a clinical diagnosis of MI. After adjustment for cardiovascular comorbidities and clinical features, age and sex were no longer associated with a clinical diagnosis of MI (eTable 2 in Supplement 1 ). In Scotland, higher cardiac troponin concentrations were associated with a clinical diagnosis of MI, and a similar association was found in Sweden ( Table 1 ).

For both type 1 and type 2 MI, the frequency of coronary angiography at 30 days was higher in patients with a clinical diagnosis compared with patients without a clinical diagnosis in Scotland (type 1: 1883 patients [75%] vs 176 patients [26%]; P  < .001; type 2: 25 patients [20%] vs 57 patients [10%]; P  < .001) (eTable 3 in Supplement 1 ) . Findings were consistent in Sweden (eTable 3 in Supplement 1 ). Similarly in both countries, use of secondary prevention was higher in patients with a clinical diagnosis of MI for both type 1 and type 2 MI.

In Scotland, the primary outcome occurred more often in patients with an adjudicated diagnosis of type 1 MI who did not have a clinical MI diagnosis compared with those with a clinical diagnosis of MI (29% vs 18%; P  < .001) ( Figure 3 ). The primary outcome for patients with type 1 MI with and without a clinical diagnosis in Sweden was similar (18% vs 16%; P  = .51). In contrast, patients with an adjudicated diagnosis of type 2 MI who did not have a clinical diagnosis of MI had a lower cumulative incidence of the primary outcome compared with patients with a clinical diagnosis (Scotland: 24% vs32%; P  < .001; Sweden: 21% vs 42%; P  < .001). Differences between groups were attenuated after adjustment for sex, age, and other known cardiovascular risk factors (eTable 4 in Supplement 1 ).

For primary analysis, we identified patients with MI if an I21 or I22 code was listed in any position. Findings were consistent in our exploratory analysis when we restricted the diagnostic code for MI to the first position, with excellent agreement between adjudicated and clinical diagnosis for type 1 MI but not for type 2 MI (eTable 5 in Supplement 1 ). Diagnostic accuracy and outcomes were similar in the cohort from Scotland when patients with STEMI were excluded (eTable 6 and eFigure 2 in Supplement 1 ). A clinical diagnosis of MI was recorded in 93% of all patients with an adjudicated diagnosis of type 1 or type 2 STEMI in Scotland, and neither sex nor age were associated with receiving a clinical diagnosis in this subgroup ( eTable 7 in Supplement 1 ). As for primary outcome, we observed similar findings for our secondary outcomes at 1 year in both cohorts (eFigures 3-6 in Supplement 1 ).

In this cohort study among consecutive patients across 2 different countries, we evaluated how the UDMI has been applied in practice. Our main finding was that fewer than 1 in 5 patients who met the diagnostic criteria for type 2 MI received the diagnosis in practice. In contrast, 4 in 5 patients with an adjudicated diagnosis of type 1 MI were identified in practice. Patients meeting the diagnostic criteria for type 1 MI but not classified as having MI in practice were more likely to be women, be older, or have had a small increase in cardiac troponin. Despite these patients being less likely to undergo coronary angiography or to receive secondary prevention, they were at similar or higher risk of subsequent MI or cardiovascular death than those with a clinical diagnosis of MI.

Our study has several strengths. First, we evaluated this research question in 2 prospective cohort studies from countries with universal health care. In both countries, hospital discharge codes are used for public health surveillance rather than financial reimbursement, reducing the risk of ascertainment bias. Second, in both cohorts the criterion standard was adjudicated according to UDMI. Third, our study comprised consecutive patients with possible MI evaluated using cardiac troponin I and T; therefore, our findings are likely to apply to health care systems using either assay.

Only a minority of patients who met the diagnostic criteria for type 2 MI received this diagnosis in clinical practice. This observation is consistent with findings from registries, which have reported that the diagnosis of MI was recorded in one-third of patients with type 2 MI identified by adjudication. 22 Patients with type 2 MI were more often treated outside the coronary care unit, which may have contributed to misclassification. 22 Together these studies suggest considerable uncertainty as to how to apply the diagnostic criteria for type 2 MI in practice. The current classification encompasses a broad range of patients, from those with coronary mechanisms of MI to those without any underlying coronary artery disease. 8 , 15 , 23 , 24 Furthermore, the diagnosis requires evidence of symptoms or signs of myocardial ischemia, which can be more difficult to ascertain in patients presenting with another acute condition. As such, alternative classifications have been proposed with more objective diagnostic criteria recognizing that MI can arise spontaneously, secondary to another condition or as a complication of a cardiac procedure. 25

Our findings raise another more fundamental question about the value of a diagnosis of type 2 MI in practice. The classification of any disease should inform the patient of their prognosis and guide the approach to treatment. 26 Currently we lack evidence-based recommendations for management and treatment of patients with type 2 MI. 9 While there is little doubt that patients with type 2 MI are at risk of major cardiovascular events, 10 , 24 until there are well-defined management and treatment implications for patients with this condition, it is likely that clinicians will prioritize management of the primary presenting condition and be less likely to recognize type 2 MI in practice.

In Scotland, patients meeting the diagnostic criteria for type 1 MI but not classified as having MI in practice were more likely to be women or to be older. However, these observed differences were not independent of differences in other clinical features, suggesting that the presence of comorbidity or magnitude of troponin increase is more likely to influence clinical diagnosis than age and sex per se. Our observations are consistent with previous work demonstrating sex- and age-associated differences in diagnosis of MI 27 - 29 and underline the need to increase awareness to prevent inequalities in care.

Misclassified patients with type 1 and type 2 MI underwent fewer investigations and were less likely to receive preventative therapies. The risk of future MI or cardiovascular death was higher or as high in patients with type 1 MI who did not receive a diagnosis of MI in practice. While we observed that patients with type 1 MI who were not diagnosed with MI in practice in Scotland remained at higher risk after adjustment for risk factors, we did not observe this in Sweden. This may be a consequence of the reliability of the primary outcome measure between 2 cohorts. All subsequent events where patients reattended with evidence of myocardial injury were adjudicated in Scotland, while we relied on ICD-10 coding to identify events in Sweden. Variation could also be due to differences in the troponin assay, diagnostic pathway, application of sex-specific criteria or the use of cardiac investigations. In contrast, we observed that patients with type 2 MI who did not receive a clinical diagnosis of MI were at lower risk of future events than those recognized in practice in both countries. It appears that clinicians are more likely to use the term MI in the setting of myocardial oxygen supply demand mismatch if they recognize the patient to be at particularly high risk of future cardiovascular events.

Hospital discharge codes for MI are based on ICD-10 rather than the UDMI. Unfortunately, ICD-10 does not recognize the 5 subtypes of MI described in the UDMI. While some health care systems or insurance providers have recently introduced an additional digit for ICD-10 codes to identify patients with type 2 MI (I21.A1) this is not universally applied and the accuracy of these codes is unknown. 30 - 32

Our study has several limitations. First, no data on race or ethnicity were available. On a national level, both cohorts included predominantly a White population, which may limit the generalizability of our findings. Second, we could not determine whether misclassification was a result of the responsible clinician not applying the diagnosis or whether it arose due to errors in hospital discharge coding. Third, we were not able to evaluate accuracy of the new ICD-10 diagnostic code for type 2 MI (I21.A1), which was introduced for billing purposes in the US in 2017, as this code is not used in either United Kingdom or Sweden.

This cohort study found that the diagnostic classification proposed by the UDMI was not consistently applied in clinical practice. Our findings suggest uncertainty remains regarding the diagnostic criteria or value of this classification in practice.

Accepted for Publication: February 13, 2024.

Published: April 8, 2024. doi:10.1001/jamanetworkopen.2024.5853

Open Access: This is an open access article distributed under the terms of the CC-BY License . © 2024 Taggart C et al. JAMA Network Open .

Corresponding Author: Nicholas L. Mills, MD, PhD, BHF Centre for Cardiovascular Science, The University of Edinburgh, Chancellor’s Building, Edinburgh EH16 4SU, United Kingdom ( [email protected] ).

Author Contributions: Dr Taggart had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Drs Taggart and Roos contributed equally.

Concept and design: Taggart, Roos, Bularga, Wereski, Chapman, Mills, Kimenai.

Acquisition, analysis, or interpretation of data: Taggart, Roos, Kadesjö, Anand, Li, Doudesis, Lee, Wereski, Lowry, Chapman, Ferry, Shah, Gard, Lindahl, Edgren, Mills, Kimenai.

Drafting of the manuscript: Taggart, Roos, Ferry, Mills, Kimenai.

Critical review of the manuscript for important intellectual content: Taggart, Roos, Kadesjö, Anand, Li, Doudesis, Lee, Bularga, Wereski, Lowry, Chapman, Shah, Gard, Lindahl, Edgren, Mills, Kimenai.

Statistical analysis: Taggart, Doudesis, Kimenai.

Obtained funding: Taggart, Mills.

Administrative, technical, or material support: Taggart, Roos, Kadesjö, Lee, Chapman, Edgren.

Supervision: Anand, Lindahl, Edgren, Mills, Kimenai.

Conflict of Interest Disclosures: Dr Wereski reported receiving grants from Novo Nordisk (paid to institution) outside the submitted work. Dr Mills reported receiving personal fees from Abbott Diagnostics, Roche Diagnostics, Siemens Healthineers, LumiraDx and grants (paid to institution) from Abbott Diagnostics, Roche Diagnostics, and Siemens Healthineers outside the submitted work. No other disclosures were reported.

Funding/Support: Dr Taggart is supported by a British Heart Foundation Clinical Research Training Fellowship (award No. FS/CRTF/21/2473). Dr Roos is supported by the Stockholm County Council (grant No. 20200935). Dr Doudesis is supported by an award from the Medical Research Council (award No. MR/N013166/1). Dr Mills is supported by the British Heart Foundation through a Chair Award (award No. CH/F/21/90010), Programme Grant (grant No. RG/20/10/34966), and a Research Excellent Award (award No. RE/18/5/34216). Dr Kimenai is supported by a British Heart Foundation Intermediate Basic Science Research Fellowship (award No. FS/IBSRF/23/25161).

Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Data Sharing Statement: See Supplement 2 .

Additional Contributions: We thank the High-STEACS Investigators for their contributions to the conception or design of the work, or the acquisition, analysis, or interpretation of data for the work. We thank Professor Martin J. Holzmann (deceased June 5, 2021) for his leadership.

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ORIGINAL RESEARCH article

This article is part of the research topic.

Emotion Dynamics: Mapping the structure and function of emotional variability

Temporal Dynamics of Positive Emotion Regulation: Insights from Facial Electromyography Provisionally Accepted

  • 1 Department of Psychology, Stanford University, United States

The final, formatted version of the article will be published soon.

Emotion regulation (ER) is a complex process that manifests gradually over time. This study investigated the temporal dynamics of ER in modifying positive emotions in terms of both negative affect (NA) and positive affect (PA) dimensions. After participants had been exposed to pleasant pictures for 8,000 ms, they received instructions to either continue viewing the picture (no regulation) or reappraise it with a neutral meaning (neutralize goal) or negative meaning (transform goal) for another 8,000 ms. We obtained corrugator supercilii and zygomaticus major electromyography (EMG) as objective measures of NA and PA. For the no-regulation condition, upon instruction onset, we observed maintained low levels of corrugator and high levels of zygomaticus EMG reactivity, indicating sustained PA activation. Compared to the no-regulation condition, for the neutralize goal, we observed no change in corrugator reactivity, which remained at a low level, while zygomaticus reduction started at 1,000 ms after instruction onset, indicating decreased PA and generation of a neutral emotional state. For the transform goal, we observed corrugator increase and zygomaticus decrease both starting at 1,500 ms after instruction onset and co-existing throughout the regulation period. These results indicate increased NA and decreased PA, relating to generation of a negative emotional state. The transform goal differed from the neutralize goal in terms of corrugator increase starting at 2,500 ms after instruction onset. Albeit simultaneous onset of changes on corrugator and zygomaticus reactivity under the transform goal, model-fitting analyses indicated that the best-fitting trajectory was one that first emphasized PA reduction until, at 3,000 ms, it turned into primary NA increase. These distinct temporal patterns highlight the possibility of effecting one-dimensional PA change with the neutralize goal and sequential two-dimensional change (first decreasing PA, then increasing NA) with the transform goal. This research sheds light on the time course of emotional change brought about by different regulatory goals.

Keywords: Emotion regulation (reappraisal), temporal dynamics analysis, Positive affect (PA), Negative affect (NA), Electromyograhy (EMG), corrugator supercilii (CS), Zygomaticus major (ZM), Time course analysis

Received: 18 Feb 2024; Accepted: 08 Apr 2024.

Copyright: © 2024 Kreibig and Gross. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: PhD. Sylvia D. Kreibig, Stanford University, Department of Psychology, Stanford, United States

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