Sources to Find Studies
All applicable sources need to be searched to locate studies and eliminate bias. Consult with a subject librarian or find suggestions from UBC Library research guides to locate key resources.
There are two key types of sources to search - licensed databases and alternate sources. Techniques for finding alternate sources include searching sources for grey literature; backward and forward reference chaining; hand searching; and contacting experts in the field.
Database Tutorials
- Medline Guided ExerciseThis tutorial provides step by step instructions for each stage of a structured search. It's intended to be a "guide on the side" - follow along or build your own!
- CINAHL Guided ExerciseStep-by-step guide to build a structured search in CINAHL.
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MEDLINE (Ovid) Tutorials
by Kyle Gailling Last Updated Feb 22, 2024 1154 views this year
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CINAHL Tutorials
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EMBASE Video Tutorials
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- Education Library Video Tutorials
- Research Skills For Engineering Students (2023 edition)
PubMed for Systematic Reviews
We recommend Ovid Medline, rather than PubMed, for systematic reviews for several reasons. Ovid Medline allows you to:
- easily read your search, because terms are on separate lines
- use adj operator for proximity searches
- discover relevant MeSH terms more easily (PubMed's mapping functionality is often more limited)
Some systematic reviews state in their methods section that they've searched both Medline and PubMed. However, there's nearly complete overlap between Ovid Medline and PubMed so there's generally not a need to search them independently.
Should you prefer to search PubMed for your systematic review, consider contacting your subject librarian for help devising your search strategy.
See also:
MEDLINE, PubMed, and PMC (PubMed Central): How are they different?
Ovid's Medline Compared To PubMed
If you are searching "Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE® Daily and Ovid MEDLINE® 1946-Present" effectively, there is no reason to ALSO search PubMed. Ask your librarian for details.
Grey Literature
Grey literature refers to materials that aren't published in a traditional way, including dissertations, conference proceedings, clinical trials, and clinical practice guidelines. These sources aren't usually covered in regular licensed databases. Below are some tools for finding grey literature.
Preprints
Preprints are manuscripts which may have been submitted to a journal, but not yet published. They have not yet gone through a formal peer review process, but some preprint servers do allow other researchers to post comments.
Preprint Repository Table
- Preprints in Europe PMCEurope PMC includes preprints from several sources, including arXiv, bioRxiv, medRxiv, PeerJ, ResearchSquare, SSRN and more. Searching via Europe PMC allows easy export of references in RIS or other formats.
- OSF PreprintsRepository of preprints in a wide variety of subjects.
- Research Preprints: Server ListDirectory of preprint repositories.
Forward and Backward Reference Chaining
Check out the citations in the reference lists of major studies. Examine what later studies have cited significant studies in these lists by searching:
- Google Scholar This link opens in a new windowWorld's largest academic search engine providing free searching to a full range of scholarly literature (ie. peer-reviewed papers, theses, books, pre-prints, abstracts, technical reports).
- citationchaserAutomatically find cited and citing references for a set of studies, and download in RIS. Based on data from The Lens (www.lens.org)
- Web of Science Core Collection This link opens in a new windowMultidisciplinary database of journal articles and conference proceedings, used for citation analysis of research. Includes access to EndNote Basic, a web-based version of EndNote.
Handsearching and Consulting Experts
Handsearching means manually looking through journals of interest to check that nothing was missed when searching licensed databases. For your topic, ensure that key journals are either adequately indexed in the databases you're searching, and if not, consider handsearching (ask your librarian if you need help determining where a journal is indexed).
Another idea for uncovering unpublished research is to identify key researchers working on your topic of interest to identify studies in process. For instance, you might be able to get additional data on a study described in a clinical trials register or conference abstract, or on a review protocol.