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After reviewing this section, the reader will:
"The term scientific literature refers to theoretical and research publications in scientific journals, reference books, textbooks, government reports, policy statements, and other materials about the theory, practice, and results of scientific inquiry. These materials and publications are produced by individuals or groups in universities, foundations, government research laboratories, and other nonprofit or for-profit organizations." (Garrard, 2017)
Scientific literature can be found in primary, secondary, and tertiary sources. When searching for answers to background and foreground questions, it is important to understand the differences between the three sources. Understanding the classification system enables prioritization of resources for the literature search and selection of the appropriate resource to answer the research topic or clinical question. It is important to remember the definitions between secondary and tertiary sources as they can sometimes be blurred, especially between different disciplines (i.e., health sciences, social sciences, humanities).
| Source Classification | Primary Sources | Secondary Sources | Tertiary Sources |
|---|---|---|---|
| Definitions |
Primary sources are the original research publications written or presented by the scientists who conducted the study. They comprise the most current biomedical literature and are an information source for secondary and tertiary sources. Consulting the primary sources to answer foreground questions allows the researcher or clinician to review and evaluate the primary sources to determine if the scientific conclusions are valid. |
Secondary sources include papers or other documents that summarize, analyze, or review the information in primary sources or other secondary sources. The researcher or clinician should consider secondary sources to answer background questions. |
Tertiary sources provide distillations, overviews, and information consolidated from the primary and secondary information. Tertiary sources serve as a resource of established knowledge and is updated when new information or knowledge is published. The researcher or clinician should also consider tertiary sources to answer background questions. |
| Sources |
Original research published in: Journals (original research, case reports, research correspondence, etc., published in peer-reviewed, non-refereed, or popular journals) Conference proceedings (papers, podium, or poster presentations at conferences, meetings, and symposia that provide the most current findings on a particular issue or problem) Clinical trials Patents Technical reports (results of technical or scientific research usually funded by the government or corporate entities) Theses or dissertations |
Overviews of previously published research: (Non-systematic) reviews (summary of primary studies) Systematic review (summary of primary studies according to a rigorous and predefined methodology) Meta-analysis (a review article that synthesizes the research results from a number of relevant articles using statistical methods) Practice guidelines (accessible from professional associations, government websites) |
Textbooks (provide synthesized evaluated information known at the time of publication and are generally published at least 2-3 years after the research on which the contents are based) Information databases (full-text, non-bibliographic databases which evaluate, review, and provide a synopsis of the literature on a specific subject, specialty or topic. These databases are well referenced and provide quick access to the primary literature. Official publications (published by government and official bodies, such as organizations, associations and agencies) |
| Examples of Sources |
Journals – Lancet, The New England Journal of Medicine, etc. Conference Literature – meeting or conference abstracts, posters, proceedings, non-published meeting papers Clinical Trials – Cochrane CENTRAL, clinicaltrials.gov Patent Applications – U.S. Patent and Trademark Office Technical Reports – Science.gov Theses/Dissertations – Library’s Theses and Dissertations Portal |
Reviews – Cochrane Database of Systematic Review Guidelines – ECRI Guidelines Trust™, Centers for Disease Control & Prevention, association guidelines or best practices |
Textbooks – Harrison's Principles of Internal Medicine, Lippincott Manual of Nursing Practice. Search the UT Southwestern Library’s catalog to check available print and online books. Information Databases – UpToDate, Micromedex, PEDro Official Publications – Federal Government Data and Statistics, Food and Drug Administration (FDA), Texas Department of State Health Services |
| Other Comments | Journal publications have a long history. Significant reports may be found in older journal articles published in print before the introduction of MEDLINE |
Other Sources include electronic communication, such as information from social media, listservs, blogs, chat, and email. These sources are useful for sharing information between colleagues and experts. Information contained in alternative literature should cite the relevant primary literature.
(Garrard, 2017; Greenhalgh, 2001; Wessel, 2019; Wright, 1998)
What are the optimal resources? To a large extent, it depends on the type of question you are asking, the comprehensiveness required, how much time you have, and readily available resources.
Why do clinicians and researchers search the free, general Internet when they have a question? The Internet is freely accessible, easy, familiar, and quick. Within seconds, most search engines retrieve hundreds (or thousands) of results based on the search keywords and ranked by relevance or other criteria. While some of the retrieved information may answer the question, it is likely that the Internet search missed relevant information.
Databases are electronic filing systems of vetted, retrievable citations from different sources, including journals, books, proceedings, etc. UT Southwestern Library subscribes to hundreds of vetted databases.
Other sources include:
Trial Registries and Trial Results Registries – study registries allow researchers to find ongoing clinical trials and studies that may have gone unpublished. Key sources include but are not limited to ClinicalTrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) portal.
Regulatory Agencies – include but are not limited to U.S. Food and Drug Administration, Occupational Safety and Health Administration, etc.
A well-defined question based on a clear understanding of the nature and scope of the research topic or clinical question allows the researcher or clinician to identify and prioritize which information resources and online databases to search. To minimize consequences of over reliance on a single database, it is recommended to search multiple databases and resources.
To get started, the following table lists suggested databases by discipline/subject. Please refer to the "Additional Resources" section below the table to access additional resources in selected subject areas.
|
Basic Sciences
|
Drugs/Pharmacy
|
Medicine
|
|
Education
|
Global Health
|
Psychiatry/Psychology
|
|
Nursing/Allied Health
|
Administration
|
Business
Legal
|
(Booth, 2012; Gerberi, Hawthorne, & Larsen, 2012; Jankowski, 2008; Patrick & Munro, 2004; Welch Medical Library Johns Hopkins University of Medicine, 2019; Wessel, 2019; Wessel, Tannery, & Epstein, 2010)
Grey literature (or gray literature) includes information or materials that are not published or indexed in the traditional databases, indexes, peer-reviewed journals, and books. These materials are referred to as grey or fugitive because they can be difficult to identify and obtain.
Examples include:
See the "Grey Literature" tab under Search (Task 5) - Systematic Review Guide - LibGuides at University of Texas Southwestern Medical Center for sources.
(Adorno, Garbee, & Marix, 2016; Booth, 2012; Grey Net International, 2019; Health Sciences Library McMaster University, 2019, Paez, 2017)
Adorno, M., Garbee, D., & Marix, M. L. (2016). Improving Literature Searches. Clin Nurse Spec, 30(2), 74-80. doi:10.1097/nur.0000000000000187
Booth, A., Papaioannou, D., Sutton, A. (2012). Systematic Approaches to a Successful Literature Review. London: Sage Publications Ltd.
Garrard, J. (2017). Health Sciences Literature Review Made Easy: The Matrix Method (Fifth Edition ed.). Burlington, MA: Jones & Bartlett Learning.
Gerberi, D., Hawthorne, D. M., & Larsen, K. E. (2012). Rethinking Responsible Literature Searching using LibGuides. Med Ref Serv Q, 31(4), 355-371. doi:10.1080/02763869.2012.723981
Greenhalgh, T. (2001). How to read a paper: the basics of evidence based medicine (Second ed. ed.). London: BMJ.
Grey Net International. (2019). GreyGuide. Retrieved from http://greyguide.isti.cnr.it/index.php
Health Sciences Library McMaster University. (2019). How Do I Find Grey Literature. Retrieved from https://libguides.mcmaster.ca/find-grey-literature
Jankowski, T. A. (2008). The Medical Library Association Essential Guide to Becoming an Expert Searcher: Proven Techniques, Strategies, and Tips for Finding Health Information. New York: Neal-Schuman Publishers.
Paez, A. (2017). Grey literature: An important resource in systematic reviews. Journal of Evidence-Based Medicine. doi. 10.1111/jebm.12265
Patrick, L. J., & Munro, S. (2004). The literature review: demystifying the literature search. Diabetes Educ, 30(1), 30-34, 36-38. doi:10.1177/014572170403000106
Welch Medical Library Johns Hopkins University of Medicine. (2019). Expert Searching. Retrieved from https://browse.welch.jhmi.edu/searching
Wessel, C. B. (2019). Responsible Literature Searching for Research: A Self-Paced Interactive Program. Retrieved from https://cme.hs.pitt.edu/ISER/app/learner/loadModule?moduleId=8381&dev=false
Wessel, C. B., Tannery, N. H., & Epstein, B. A. (2010). Evaluation of a self-paced learning module to teach responsible literature searching for research. J Med Libr Assoc, 98(1), 82-85. doi:10.3163/1536-5050.98.1.020
Wright, S. G. L., Rhonda Lea; Kendrach, Michael G. (1998). A Review of the Three Types of Biomedical Literature and the Systematic Approach to Answer a Drug Information Request Journal of Pharmacy Practice, 11(3), 148-162. doi:10.1177/089719009801100307