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A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process.
What is the purpose of literature review , a. habitat loss and species extinction: , b. range shifts and phenological changes: , c. ocean acidification and coral reefs: , d. adaptive strategies and conservation efforts: .
What is a literature review .
A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.
A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2
1. Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge.
2. Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field.
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3. Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research.
4. Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered.
5. Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research.
6. Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature.
Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic.
Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies:
Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements.
Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources.
The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems.
Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning.
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Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements.
Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review.
Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria.
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Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research.
Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1
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The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a good literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. By combining effortless research with an easy citation process, Paperpal Research streamlines the literature review process and empowers you to write faster and with more confidence. Try Paperpal Research now and see for yourself.
A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.
Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.
Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic.
Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods.
Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers. Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved. Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic. Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings. Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject. It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.
The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review: Introduction: Provide an overview of the topic. Define the scope and purpose of the literature review. State the research question or objective. Body: Organize the literature by themes, concepts, or chronology. Critically analyze and evaluate each source. Discuss the strengths and weaknesses of the studies. Highlight any methodological limitations or biases. Identify patterns, connections, or contradictions in the existing research. Conclusion: Summarize the key points discussed in the literature review. Highlight the research gap. Address the research question or objective stated in the introduction. Highlight the contributions of the review and suggest directions for future research.
Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows:
Annotated Bibliography | Literature Review | |
Purpose | List of citations of books, articles, and other sources with a brief description (annotation) of each source. | Comprehensive and critical analysis of existing literature on a specific topic. |
Focus | Summary and evaluation of each source, including its relevance, methodology, and key findings. | Provides an overview of the current state of knowledge on a particular subject and identifies gaps, trends, and patterns in existing literature. |
Structure | Each citation is followed by a concise paragraph (annotation) that describes the source’s content, methodology, and its contribution to the topic. | The literature review is organized thematically or chronologically and involves a synthesis of the findings from different sources to build a narrative or argument. |
Length | Typically 100-200 words | Length of literature review ranges from a few pages to several chapters |
Independence | Each source is treated separately, with less emphasis on synthesizing the information across sources. | The writer synthesizes information from multiple sources to present a cohesive overview of the topic. |
References
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By Aaron Tay, Lead, Data Services
Getting into a new research topic and unsure where to start? Wouldn’t it be great if there was a good map of the literature done by someone already, waiting for you to refer to? Indeed, there are many rich sources that you can consider using to kick start your literature review.
These include
But such items are not easily found; how do you find them? As dissertations and theses are relatively easily found these days, I will focus more on the first three article or document types.
For some databases it is as simple as typing in a general keyword and choosing the appropriate filter. Alternatively in some databases you can go to advanced search to preselect the document type you want to see.
Some of these databases include
For some databases like ERIC , the Educational Resources Information Center which is good for education literature, you can use the thesaurus which has subjects like Literature Reviews , combine that with your topic and you can do a search for literature reviews .
The first three in the list are good for cross-disciplinary searches, while the remaining are discipline specific. Please consult your research librarian if you need more specific advice.
Unfortunately, not every academic database provides an easy way to filter to reviews or systematic reviews. A particularly important one is Google Scholar, which is generally recognised as the single biggest sources of academic content but does not seem to have a filter for this type of content.
[New as of Jan 2022] Google Scholar now has a “Review Articles” filter! You can use the built-in filter or continue to use the search based method below which gives different results and may give trade-offs in terms of precision and recall of the results.
How then does one search for reviews in Google Scholar? One can simulate a filter by crafting a suitable search strategy for this.
Assuming for example the topic of interest is creativity, you can do a search like this < creativity review OR meta-analysis OR "a survey" > in Google Scholar.
This generally works because most reviews, systematic reviews or meta-analysis would typically have those terms in the title and Google Scholar tends to prioritize matching keywords in the title, resulting in finding what you need in the top few results.
However, if you find that Google Scholar is generally giving you irrelevant results you can tighten up the search by restricting keywords to be matched in the title with the <intitle:> command.
Try < creativity intitle:review OR intitle:meta-analysis OR intitle:"a survey"> in Google Scholar
In China, and lacking access to Google Scholar?
Use Baidu Xueshu (百度学术) / Baidu Academic or Scholar which is their answer to Google Scholar to automatically find review papers with their analysis function .
If the above tools are still not sufficient, you can try using Connected Papers , which we covered in an earlier Research Radar piece .
What was not mentioned in the piece was that Connected Papers can not only generate a map of related paper from one relevant “seed” paper, it can also attempt to find review papers with the “Derivative Works” function that attempts to “find surveys of the field or recent relevant works which were inspired by many papers in the graph”
While this doesn’t always work, it is worth a try.
Finally, if all else fails, you can try using the method I outlined in this medium post which use a saved search strategy in 2D search to query Lens.org . You do not need to fully understand the complex search strategy I have constructed, simply change the topic box that has the word “Creativity” with your topic and run the search.
Once you have located review papers, systematic reviews etc, the sky’s the limit. You can mine the literature review for useful references of course. But review papers are often a magnet for citations and as such you can also find newer relevant papers by doing citation searching .
By now you will no doubt have more than enough relevant literature to read, but if you need more you can use them as “seed papers” in the literature mapping tools we introduced in past Research Radar pieces like Connected Papers, Inciteful. Litmaps or ResearchRabbit to find even more relevant papers!
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Marco pautasso.
1 Centre for Functional and Evolutionary Ecology (CEFE), CNRS, Montpellier, France
2 Centre for Biodiversity Synthesis and Analysis (CESAB), FRB, Aix-en-Provence, France
Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications [1] . For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively [2] . Given such mountains of papers, scientists cannot be expected to examine in detail every single new paper relevant to their interests [3] . Thus, it is both advantageous and necessary to rely on regular summaries of the recent literature. Although recognition for scientists mainly comes from primary research, timely literature reviews can lead to new synthetic insights and are often widely read [4] . For such summaries to be useful, however, they need to be compiled in a professional way [5] .
When starting from scratch, reviewing the literature can require a titanic amount of work. That is why researchers who have spent their career working on a certain research issue are in a perfect position to review that literature. Some graduate schools are now offering courses in reviewing the literature, given that most research students start their project by producing an overview of what has already been done on their research issue [6] . However, it is likely that most scientists have not thought in detail about how to approach and carry out a literature review.
Reviewing the literature requires the ability to juggle multiple tasks, from finding and evaluating relevant material to synthesising information from various sources, from critical thinking to paraphrasing, evaluating, and citation skills [7] . In this contribution, I share ten simple rules I learned working on about 25 literature reviews as a PhD and postdoctoral student. Ideas and insights also come from discussions with coauthors and colleagues, as well as feedback from reviewers and editors.
How to choose which topic to review? There are so many issues in contemporary science that you could spend a lifetime of attending conferences and reading the literature just pondering what to review. On the one hand, if you take several years to choose, several other people may have had the same idea in the meantime. On the other hand, only a well-considered topic is likely to lead to a brilliant literature review [8] . The topic must at least be:
Ideas for potential reviews may come from papers providing lists of key research questions to be answered [9] , but also from serendipitous moments during desultory reading and discussions. In addition to choosing your topic, you should also select a target audience. In many cases, the topic (e.g., web services in computational biology) will automatically define an audience (e.g., computational biologists), but that same topic may also be of interest to neighbouring fields (e.g., computer science, biology, etc.).
After having chosen your topic and audience, start by checking the literature and downloading relevant papers. Five pieces of advice here:
The chances are high that someone will already have published a literature review ( Figure 1 ), if not exactly on the issue you are planning to tackle, at least on a related topic. If there are already a few or several reviews of the literature on your issue, my advice is not to give up, but to carry on with your own literature review,
The bottom-right situation (many literature reviews but few research papers) is not just a theoretical situation; it applies, for example, to the study of the impacts of climate change on plant diseases, where there appear to be more literature reviews than research studies [33] .
When searching the literature for pertinent papers and reviews, the usual rules apply:
If you read the papers first, and only afterwards start writing the review, you will need a very good memory to remember who wrote what, and what your impressions and associations were while reading each single paper. My advice is, while reading, to start writing down interesting pieces of information, insights about how to organize the review, and thoughts on what to write. This way, by the time you have read the literature you selected, you will already have a rough draft of the review.
Of course, this draft will still need much rewriting, restructuring, and rethinking to obtain a text with a coherent argument [11] , but you will have avoided the danger posed by staring at a blank document. Be careful when taking notes to use quotation marks if you are provisionally copying verbatim from the literature. It is advisable then to reformulate such quotes with your own words in the final draft. It is important to be careful in noting the references already at this stage, so as to avoid misattributions. Using referencing software from the very beginning of your endeavour will save you time.
After having taken notes while reading the literature, you will have a rough idea of the amount of material available for the review. This is probably a good time to decide whether to go for a mini- or a full review. Some journals are now favouring the publication of rather short reviews focusing on the last few years, with a limit on the number of words and citations. A mini-review is not necessarily a minor review: it may well attract more attention from busy readers, although it will inevitably simplify some issues and leave out some relevant material due to space limitations. A full review will have the advantage of more freedom to cover in detail the complexities of a particular scientific development, but may then be left in the pile of the very important papers “to be read” by readers with little time to spare for major monographs.
There is probably a continuum between mini- and full reviews. The same point applies to the dichotomy of descriptive vs. integrative reviews. While descriptive reviews focus on the methodology, findings, and interpretation of each reviewed study, integrative reviews attempt to find common ideas and concepts from the reviewed material [12] . A similar distinction exists between narrative and systematic reviews: while narrative reviews are qualitative, systematic reviews attempt to test a hypothesis based on the published evidence, which is gathered using a predefined protocol to reduce bias [13] , [14] . When systematic reviews analyse quantitative results in a quantitative way, they become meta-analyses. The choice between different review types will have to be made on a case-by-case basis, depending not just on the nature of the material found and the preferences of the target journal(s), but also on the time available to write the review and the number of coauthors [15] .
Whether your plan is to write a mini- or a full review, it is good advice to keep it focused 16 , 17 . Including material just for the sake of it can easily lead to reviews that are trying to do too many things at once. The need to keep a review focused can be problematic for interdisciplinary reviews, where the aim is to bridge the gap between fields [18] . If you are writing a review on, for example, how epidemiological approaches are used in modelling the spread of ideas, you may be inclined to include material from both parent fields, epidemiology and the study of cultural diffusion. This may be necessary to some extent, but in this case a focused review would only deal in detail with those studies at the interface between epidemiology and the spread of ideas.
While focus is an important feature of a successful review, this requirement has to be balanced with the need to make the review relevant to a broad audience. This square may be circled by discussing the wider implications of the reviewed topic for other disciplines.
Reviewing the literature is not stamp collecting. A good review does not just summarize the literature, but discusses it critically, identifies methodological problems, and points out research gaps [19] . After having read a review of the literature, a reader should have a rough idea of:
It is challenging to achieve a successful review on all these fronts. A solution can be to involve a set of complementary coauthors: some people are excellent at mapping what has been achieved, some others are very good at identifying dark clouds on the horizon, and some have instead a knack at predicting where solutions are going to come from. If your journal club has exactly this sort of team, then you should definitely write a review of the literature! In addition to critical thinking, a literature review needs consistency, for example in the choice of passive vs. active voice and present vs. past tense.
Like a well-baked cake, a good review has a number of telling features: it is worth the reader's time, timely, systematic, well written, focused, and critical. It also needs a good structure. With reviews, the usual subdivision of research papers into introduction, methods, results, and discussion does not work or is rarely used. However, a general introduction of the context and, toward the end, a recapitulation of the main points covered and take-home messages make sense also in the case of reviews. For systematic reviews, there is a trend towards including information about how the literature was searched (database, keywords, time limits) [20] .
How can you organize the flow of the main body of the review so that the reader will be drawn into and guided through it? It is generally helpful to draw a conceptual scheme of the review, e.g., with mind-mapping techniques. Such diagrams can help recognize a logical way to order and link the various sections of a review [21] . This is the case not just at the writing stage, but also for readers if the diagram is included in the review as a figure. A careful selection of diagrams and figures relevant to the reviewed topic can be very helpful to structure the text too [22] .
Reviews of the literature are normally peer-reviewed in the same way as research papers, and rightly so [23] . As a rule, incorporating feedback from reviewers greatly helps improve a review draft. Having read the review with a fresh mind, reviewers may spot inaccuracies, inconsistencies, and ambiguities that had not been noticed by the writers due to rereading the typescript too many times. It is however advisable to reread the draft one more time before submission, as a last-minute correction of typos, leaps, and muddled sentences may enable the reviewers to focus on providing advice on the content rather than the form.
Feedback is vital to writing a good review, and should be sought from a variety of colleagues, so as to obtain a diversity of views on the draft. This may lead in some cases to conflicting views on the merits of the paper, and on how to improve it, but such a situation is better than the absence of feedback. A diversity of feedback perspectives on a literature review can help identify where the consensus view stands in the landscape of the current scientific understanding of an issue [24] .
In many cases, reviewers of the literature will have published studies relevant to the review they are writing. This could create a conflict of interest: how can reviewers report objectively on their own work [25] ? Some scientists may be overly enthusiastic about what they have published, and thus risk giving too much importance to their own findings in the review. However, bias could also occur in the other direction: some scientists may be unduly dismissive of their own achievements, so that they will tend to downplay their contribution (if any) to a field when reviewing it.
In general, a review of the literature should neither be a public relations brochure nor an exercise in competitive self-denial. If a reviewer is up to the job of producing a well-organized and methodical review, which flows well and provides a service to the readership, then it should be possible to be objective in reviewing one's own relevant findings. In reviews written by multiple authors, this may be achieved by assigning the review of the results of a coauthor to different coauthors.
Given the progressive acceleration in the publication of scientific papers, today's reviews of the literature need awareness not just of the overall direction and achievements of a field of inquiry, but also of the latest studies, so as not to become out-of-date before they have been published. Ideally, a literature review should not identify as a major research gap an issue that has just been addressed in a series of papers in press (the same applies, of course, to older, overlooked studies (“sleeping beauties” [26] )). This implies that literature reviewers would do well to keep an eye on electronic lists of papers in press, given that it can take months before these appear in scientific databases. Some reviews declare that they have scanned the literature up to a certain point in time, but given that peer review can be a rather lengthy process, a full search for newly appeared literature at the revision stage may be worthwhile. Assessing the contribution of papers that have just appeared is particularly challenging, because there is little perspective with which to gauge their significance and impact on further research and society.
Inevitably, new papers on the reviewed topic (including independently written literature reviews) will appear from all quarters after the review has been published, so that there may soon be the need for an updated review. But this is the nature of science [27] – [32] . I wish everybody good luck with writing a review of the literature.
Many thanks to M. Barbosa, K. Dehnen-Schmutz, T. Döring, D. Fontaneto, M. Garbelotto, O. Holdenrieder, M. Jeger, D. Lonsdale, A. MacLeod, P. Mills, M. Moslonka-Lefebvre, G. Stancanelli, P. Weisberg, and X. Xu for insights and discussions, and to P. Bourne, T. Matoni, and D. Smith for helpful comments on a previous draft.
This work was funded by the French Foundation for Research on Biodiversity (FRB) through its Centre for Synthesis and Analysis of Biodiversity data (CESAB), as part of the NETSEED research project. The funders had no role in the preparation of the manuscript.
What is a literature review.
A literature review is a summary of the published work in a field of study. This can be a section of a larger paper or article, or can be the focus of an entire paper. Literature reviews show that you have examined the breadth of knowledge and can justify your thesis or research questions. They are also valuable tools for other researchers who need to find a summary of that field of knowledge.
Unlike an annotated bibliography, which is a list of sources with short descriptions, a literature review synthesizes sources into a summary that has a thesis or statement of purpose—stated or implied—at its core.
Step 1: define your research scope.
Ask us if you have questions about refining your topic, search methods, writing tips, or citation management.
Start by searching broadly. Literature for your review will typically be acquired through scholarly books, journal articles, and/or dissertations. Develop an understanding of what is out there, what terms are accurate and helpful, etc., and keep track of all of it with citation management tools . If you need help figuring out key terms and where to search, ask us .
Use citation searching to track how scholars interact with, and build upon, previous research:
Key to your literature review is a critical analysis of the literature collected around your topic. The analysis will explore relationships, major themes, and any critical gaps in the research expressed in the work. Read and summarize each source with an eye toward analyzing authority, currency, coverage, methodology, and relationship to other works. The University of Toronto's Writing Center provides a comprehensive list of questions you can use to analyze your sources.
Divide the available resources that pertain to your research into categories reflecting their roles in addressing your research question. Possible ways to categorize resources include organization by:
Regardless of the division, each category should be accompanied by thorough discussions and explanations of strengths and weaknesses, value to the overall survey, and comparisons with similar sources. You may have enough resources when:
Undergraduate student resources.
Onesearch library catalog.
Depending on your assignment or project, the literature you review may include published books and journal articles as well as what librarians call gray literature (e.g., government reports, working papers produced by think tanks, and dissertations and theses).
Once you have a few appropriate sources, look at their bibliographies, references, notes, and footnotes to find additional important works in the field. If you find that particular authors or works are cited again and again in your reading, be sure to add them to your list.
Some general tools for finding resources appear below. Please consult our research guides for recommended databases and other resources tailored to your subject and for tips on using Zotero to manage your research.
Use OneSearch to find books, E-books, articles, videos, and more. Use drop-down menus, facets, and the advanced search function to apply limits to your search.
Be sure to put phrases in quotes, and use the + sign when you have more than one keyword:
"civil rights movement"
+women +"Middle Ages"
The literature review section of an article is a summary or analysis of all the research the author read before doing his/her own research. This section may be part of the introduction or in a section called Background. It provides the background on who has done related research, what that research has or has not uncovered and how the current research contributes to the conversation on the topic. When you read the lit review ask:
The lit review is also a good place to find other sources you may want to read on this topic to help you get the bigger picture.
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10-Sep-2024 - Last updated on 11-Sep-2024 at 12:22 GMT
The new paper from the ABC-AHP-NCNPR Botanical Adulterants Prevention Program (BAPP) found that the second highest estimated adulteration rate was for powdered plant materials or extracts of black cohosh ( Actaea racemosa ) root/rhizome with 42.2%, followed by echinacea ( Echinacea angustifolia, E. pallida , and E. purpurea ) herb and/or root with 28.5%.
Concerning results were also observed for elder ( Sambucus nigra ) and turmeric ( Curcuma longa ) rhizome, with 17.1% and 16.5%, respectively, according to findings published in Natural Product Reports.
These five botanicals are among the top selling herbal supplements in the market. Data from the American Botanical Council (ABC) Herb Market Report for 2022 indicate that sales of supplements formulated with these botanicals accounted for over $526 million in the U.S. mainstream and natural channels ( HerbalGram #139 ).
The review included a total of 77 publications and 2,995 samples across the five botanicals in the United States and international markets. The paper is authored by natural products pharmacology expert Nilüfer Orhan, PhD, ABC Chief Science Officer and BAPP Director Stefan Gafner, PhD, and Founder and Executive Eirector of ABC and Founder of BAPP Mark Blumenthal.
“Adulteration and fraud are unfortunate facts of commerce,” Blumenthal said. “The question is to what extent does it affect the current market for herbal dietary supplements and related natural plant- and fungal-based ingredients?
Dr. Ikhlas Khan, director of the National Center for Natural Products Research (NCNPR) at the University of Mississippi, told NutraIngredients that the new review illustrates the complexity of discovering the adulteration in well-known herbs. "Just think about the herbs that are not well studied and not well known, and it provides a picture of the adulteration level of marketed products," he said.
The review highlights the many challenges and limitations in determining the accurate number of adulterated products in a specific market.
For example, Orhan, Gafner and Blumenthal noted that results from comprehensive testing/analysis of all products sold in a geographic region are not available, criteria of what exactly represents adulteration vary from author to author, and some of the laboratory analytical methods used to determine the presence of adulteration may not be fit for purpose.
“The numbers obtained for the extent of adulteration of the five botanicals investigated for this systematic review may not be representative for the overall adulteration rate in the global herbal dietary and food supplement industry, but it is clear that adulteration of botanical ingredients is a problem and impacts a substantial portion of products sold as dietary or food supplements,” Dr. Gafner said.
The data indicated that products sold as licensed or registered herbal medicines, as is the case in many European countries, were all found to be authentic (not adulterated), contrary to products sold as dietary or food supplements.
“This highlights the importance of regulatory frameworks that mandate quality control and proper identity analysis to ensure the effectiveness and safety of botanical products (although safety concerns have not been documented in most of the published literature with respect to these five botanicals),” wrote Orhan, Gafner and Blumenthal.
“Quality control methods used by suppliers, manufacturers, researchers and regulators need to be sufficiently specific to detect possible adulterants in botanical ingredients and produce high-quality authentic products.
“There are numerous examples where some analytical methods used in industry quality control or government regulatory laboratories have been shown to be inadequate to detect adulteration and properly authenticate the botanical material(s). For this reason, BAPP has published a series of extensively peer-reviewed Laboratory Guidance Documents that evaluate the fitness for purpose of various analytical methods employed for some botanicals that BAPP has determined are subject to adulteration.”
Commenting independently on the review’s findings, Daniel Fabricant, PhD, president and CEO of the Natural Products Association (NPA), told us: "These are important issues, and it's great to have this initiative [BAPP], but to ultimately move the needle FDA needs to be getting to the right number of facilities and putting the force of law behind their inspections.
"I appreciate ABC trying to put a number on this, but we then need to have engagement with FDA. Is FDA going to those companies and facilities where there are problems?"
The new review is the 90th peer-reviewed publication published by the ABC (American Botanical Council)-AHP (American Herbal Pharmacopoeia)-NCNPR (National Center for Natural Products Research at the University of Mississippi) Botanical Adulterants Prevention Program (BAPP).
BAPP publications confirm that almost 30 (so far) of botanicals are subject to adulteration. More information is available HERE .
Source: Natural Product Reports 2024; doi: https://doi.org/10.1039/D4NP00014E “Estimating the extent of adulteration of the popular herbs black cohosh, echinacea, elder berry, ginkgo, and turmeric – its challenges and limitations” Authors: N. Orhan, S. Gafner, M. Blumenthal
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Google Scholar provides a simple way to broadly search for scholarly literature. Search across a wide variety of disciplines and sources: articles, theses, books, abstracts and court opinions.
Literature Review: The What, Why and How-to Guide — Strategies to Find Sources This guide will help you understand what is a Literature Review, why it is important and how it is done.
Find literature reviews on your topic Reading review articles is a good way to get an overview of the current research on a topic. The reviews will include key articles that you can follow up.
Learn how to find high-quality, relevant articles and resources for your literature review, the smart way. Free template included.
Finding The Literature. Research literature is vast. In the English language alone, over 2.5 million articles are published in peer reviewed journals each year. Sifting through the books and journals to find the most relevant research is challenging, but some of the resources on this page can help you. To start, write down your research ...
This guide will help get you started with searching for information for your literature review.
A literature review is a survey of scholarly knowledge on a topic. Our guide with examples, video, and templates can help you write yours.
A literature review is a review and synthesis of existing research on a topic or research question. A literature review is meant to analyze the scholarly literature, make connections across writings and identify strengths, weaknesses, trends, and missing conversations. A literature review should address different aspects of a topic as it ...
It is not enough for a review to be a summary of the latest growth in the literature: the most interesting reviews instead provide a discussion about disagreements in the field.
Literature reviews are also written as standalone articles as a way to survey a particular research topic in-depth. This type of literature review looks at a topic from a historical perspective to see how understanding of the topic has change throughout time.
Literature reviews can be narrative or systematic, with narrative reviews aiming to provide a descriptive overview of selected literature, without undertaking a systematic literature search.
It's important to know how to find relevant sources when writing a research paper, literature review, or systematic review. The types of sources you need
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Second, the paper considers five steps for developing a review: defining the main topic, searching the literature, analyzing the results, writing the review and reflecting on the writing. Ultimately, this study proposes a twelve-item LR checklist.
How to guide for researching and managing the literature review. Use databases and advanced search strategies to find sources.
What is a literature review? A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question. That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.
Writing a Literature Review. A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and ...
A literature review is a written summary of the existing published research on a topic. A literature review can be brief (a section in a larger article) or it can be an entire article unto itself. The purpose of a literature review is to provide an overview of the current knowledge on a topic, and/or to provide a context for new research.
A literature review is a comprehensive analysis of existing research on a topic, identifying trends, gaps, and insights to inform new scholarly contributions. Read this comprehensive article to learn how to write a literature review, with examples.
3 ways to find review papers, systematic reviews, meta-analysis, and other rich sources of references to kick start your literature review 30 Sep 2021
Reviewing the literature requires the ability to juggle multiple tasks, from finding and evaluating relevant material to synthesising information from various sources, from critical thinking to paraphrasing, evaluating, and citation skills [7]. In this contribution, I share ten simple rules I learned working on about 25 literature reviews as a PhD and postdoctoral student. Ideas and insights ...
What is a literature review? A literature review is a summary of the published work in a field of study. This can be a section of a larger paper or article, or can be the focus of an entire paper. Literature reviews show that you have examined the breadth of knowledge and can justify your thesis or research questions. They are also valuable tools for other researchers who need to find a ...
Depending on your assignment or project, the literature you review may include published books and journal articles as well as what librarians call gray literature (e.g., government reports, working papers produced by think tanks, and dissertations and theses).. Once you have a few appropriate sources, look at their bibliographies, references, notes, and footnotes to find additional important ...
The literature review section of an article is a summary or analysis of all the research the author read before doing his/her own research. This section may be part of the introduction or in a section called Background. It provides the background on who has done related research, what that research has or has not uncovered and how the current ...
This guide offers information on what a literature review is, how to go about conducting one, and links to library resources that will help you with the process. Undergraduate Research for Students: Literature Reviews. A literature review is exploring research that has been done directly on the topic you have chosen. Conducting a literature ...
Purpose-The purpose of this study is to conduct a comprehensive systematic literature review using bibliometric approach to investigate the academic structure of World Trade Organization Dispute ...
A new systematic literature review of five popular botanical ingredients indicates a wide range of estimated adulteration rates, with the highest reported for Ginkgo leaf extract samples at 56.7%.