What is grey literature and how do you find and cite it?

Direct answer: Grey literature is material produced by government, academia, business and industry in print and electronic formats that commercial publishers do not control (Schöpfel, 2011). The 2004 postscript adds that publishing is not the primary activity of the body producing it. Gray is the American spelling, and sources use both.

The Luxembourg wording is the one most reviews quote. Paez (2017) repeats it and then explains why it matters for evidence synthesis, while Adams et al. (2017) describe the same territory for management research as a diverse and heterogeneous body of material made public outside traditional academic peer review. Peer review is therefore the practical dividing line for many students, although the formal definition turns on commercial control rather than on review.

Two edge cases deserve care. Some theses and dissertations are rigorously reviewed and may be of high quality (Paez, 2017), so grey does not mean weak. Conference material is also mixed: Queen's University Belfast Library notes that some conference proceedings are formally published and so do not count as grey literature, which means you must check the publisher before labelling a source (see QUB Library's grey literature guide).

Direct answer: Common examples include government and agency reports, policy documents, theses and dissertations, working papers, preprints, company reports, conference abstracts, and blogs or social media posts (Adams et al., 2017; Lefebvre et al., 2025). The table groups them by what each type is typically used for.

Adams et al. (2017) list dissertations, policy documents, preprints, publications from governmental agencies, blogs and social media, working papers and company reports in their table of grey literature types, drawn from a sample of 140 management systematic reviews. Cochrane authors add reports, dissertations, theses and conference abstracts as the sources reviewers should consider (Lefebvre et al., 2025).

Direct answer: Grey literature reduces publication bias, the tendency for studies with positive findings to reach print more often than null or negative ones. Paez (2017) reports that removing it from some meta-analyses produced 15% larger estimates of treatment effects, so leaving it out can bias conclusions toward whatever got published.

Paez states the problem directly: "Publication bias refers to the propensity for only studies reporting positive findings to be published, and may skew the results of the meta-analysis and systematic review" (Paez, 2017, p. 234). The same review adds that removing gray literature from some meta-analyses results in 15% larger estimates of treatment effects and less precise effect-size estimates (Paez, 2017). The UCL Library guide makes the same point in plain terms, saying grey literature often contains null or negative findings that never reach commercial publication (UCL Library Services, n.d.). The University of Cambridge Subject Libraries (n.d.) warn that leaving it out risks biasing your results.

A fair reading also needs the counterweight. The Cochrane Handbook reports that Hartling et al. found unpublished studies rarely changed the conclusions of the reviews they sampled, although the effect may matter when few relevant studies exist or when questionable vested interests shape the published record (Lefebvre et al., 2025). For a coursework literature review the same UCL guide says your remit might not require it, so ask your supervisor how far your search should reach (UCL Library Services, n.d.). Our guide to writing a literature review explains how many sources a review needs.

Direct answer: Start with library-guide databases and targeted web searching. UK guides point to Overton, ProQuest Dissertations and Theses Global, EThOS (check it is currently available) and Google operators such as site:gov.uk (University of Cambridge Subject Libraries, n.d.; UCL Library Services, n.d.). Australian guides add Trove, the Analysis and Policy Observatory and data.gov.au.

Search operators are the cheapest technique. UCL suggests limiting searches to domains such as site:.gov.uk or site:nhs.uk (UCL Library Services, n.d.), and Queen's University Belfast Library shows how a search such as "coastal erosion" site:gov.uk filetype:pdf can surface government reports and shoreline management plans. Monash University Library lists Trove, the Analysis and Policy Observatory, Overton and data.gov.au in its grey sources guide, and the University of Edinburgh Library adds Policy Commons and BASE in its finding grey literature guide.

Be realistic about coverage. Paez (2017) notes that there is no accepted, gold standard method for conducting rigorous grey literature searches, so record every database, search string and date in your search log. That log is what lets a marker see that your gaps are deliberate.

Direct answer: Use the AACODS checklist, designed to enable evaluation and critical appraisal of grey literature (Tyndall, 2010). Its 6 criteria are Authority, Accuracy, Coverage, Objectivity, Date and Significance. Ask the questions in the table of every report, thesis or web document before you rely on it.

The Authority, Objectivity, Date and Significance wording above is quoted from Tyndall (2010), and the checklist itself holds the full prompts for Accuracy and Coverage. Queen's University Belfast Library gives the general principle: researchers should critically evaluate the quality, methodology, authority and reliability of each source.

In practice, write 1 short appraisal note per source. A government statistics release will usually score well on Authority and Date, while a campaign group's report may need a clear flag on Objectivity. Noting that weakness in your text, and saying how you handled it, is exactly the critical reading markers reward.

Direct answer: Cite grey literature by its document type. APA Style groups reports, white papers and fact sheets under "Reports and Gray Literature", with separate patterns for dissertations and preprints (American Psychological Association, n.d.). Give author, year, title and URL, and omit the publisher when it matches the author.

The omit-the-publisher rule comes from library guides that summarise APA, so treat it as a cross-check against the official examples. The official pages also warn that a report on a government website uses the reports category, whereas a page that is not a report uses the webpages category (American Psychological Association, n.d.).

For the in-text form, use the author-date pattern you already know. A report by a group author is cited with the organisation's full name in place of an author, and a report with individual authors is cited by their surnames. If you are weighing APA against Harvard for your course, read APA 7th vs Harvard referencing first.

Most students search for grey literature alone, and the skill is worth building yourself. A mentor can still save time on the parts that are hard to see from inside a project: whether your search strategy covers the right repositories, whether a source you found passes the AACODS questions, and whether your search log would convince a marker. Through thesis and dissertation mentoring at MAAS, the student does the searching, reading and writing, and a mentor guides the strategy and reviews the work you produce. There is no ghost work and no promise about results, because your supervisor and your institution decide those. Share your brief, your supervisor's expectations and your search log in the first session so the mentor can respond to your actual assignment.