Supplementary searching is critical for a scoping review, even more so than for other types of reviews. This is because the purpose of a scoping review is to determine the full scope of the literature on your topic. This means searching for things outside of the databases, which are limited in scope and may exclude relevant research.
References
Review works cited lists from similar reviews and from the articles that have met your inclusion criteria.
Cited Papers
Use Google Scholar or Web of Science to review studies that have cited the articles included in your study.
Handsearch Specific Journals
Manually browse through journals that often publish studies of interest to your review.
Clinical Trials
Not all clinical trials end in publications. Clinical Trial Registries help you locate otherwise unpublished or incomplete trials.
Dissertations & Theses
Reports and conference papers
Look for conference proceedings from relevant conferences and associations. Scan publication lists from related research centers and institutes.
Gray Literature
Though Google and Google Scholar searches will not be part of your systematic methods, Google can be used to find publications from organizations, centers and institutes of interest. Google Scholar may help turn up additional gray literature (see Document Types in Grey Literature) and some journal articles that may have been missed in the systematic search. See also:
Contact Experts: Reach out to scholars that do research on your topic and solicit publications or data that may not have been formally published.
It's important to keep a clear record of your supplementary search strategies and results. Note just where and how you searched, and which included sources were found via these strategies.
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