What Is Gray Literature?
Gray literature, spelled grey in some countries, is information produced by organizations outside the traditional commercial and academic publishing channels. It includes materials that are not controlled by publishers and are often not indexed in standard databases. Examples are government reports, technical papers, policy briefs, working papers, theses and dissertations, conference papers, white papers, clinical trial registries and statistical releases.
Types and examples
- Government and agency reports: statistics, evaluations, guidelines and inquiries.
- Nonprofit and think tank publications: policy studies and research summaries.
- Working papers and preprints, shared before formal publication.
- Theses and dissertations.
- Conference proceedings and presentations.
- Technical reports and standards from companies and research institutes.
- Newsletters, fact sheets and websites from professional bodies.
- Clinical trial registries and datasets.
Why it matters
Gray literature can be recent, specific and practical. It may include data and perspectives that are not found in journals, such as local evaluations or negative results that journals rarely publish. In systematic reviews, including gray literature helps reduce publication bias, because studies with significant results are more likely to appear in journals.
Challenges
- Quality varies, since many items are not peer reviewed.
- Bias: organizations may have an agenda.
- Discoverability: items can be scattered and poorly indexed.
- Permanence: websites change and documents disappear.
- Citation: details such as authors and dates may be unclear.
Evaluating it
Ask about the source and its purpose.
- Who produced it, and what is their expertise?
- Why was it created, and for whom?
- Are methods and sources explained?
- Is the data transparent and the date clear?
- Does other evidence support it?
- Is there any conflict of interest?
Finding it
Use library gray literature collections, specialized databases, government portals, institutional repositories and targeted web searches with filters for file type or domain. Librarians can help with search strategies. Record where and when you accessed each item.
Citing
Cite gray literature as you would other sources, following your style guide for reports and web documents, and include the organization as author if no individual is named.
Related terms
See peer review, primary source, secondary source, preprint and scholarly journal.
Frequently asked questions
Is gray literature reliable?
It varies. Some, such as government and agency reports, can be authoritative, while other items may be unreviewed or biased. Evaluate the author, purpose, method and evidence.
Why use gray literature in research?
It can include recent findings, practical data and negative results that journals may not publish, and it reduces publication bias in reviews.
How do I find gray literature?
Search government and organization websites, institutional repositories, thesis databases, conference proceedings and library gray literature collections, and ask a librarian.