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What is Grey literature

Grey/Gray literature is essentially any information that is not produced by commercial publishers.

The Twelfth International Conference on Grey Literature 2010 definition:

"Grey literature stands for manifold document types produced on all levels of government, academics, business and industry in print and electronic formats that are protected by intellectual property rights, of sufficient quality to be collected and preserved by libraries and institutional repositories, but not controlled by commercial publishers; i.e. where publishing is not the primary activity of the producing body."

For example, conference abstracts and proceedings, unpublished trial data; government publications; reports (such as white papers, working papers, internal documentation); dissertations/theses; patents, presentations, regulatory data; and policies & procedures.

Why search grey literature?

Grey literature is an important source of information when conducting a large-scale review. It includes a wide range of documents not produced by commercial publisher's. This does mean that it can be difficult to systematically search for relevant evidence, however, public health research may only be available via these sources.

If you are struggling to find sources cited in a piece of grey literature, it may be available via interlibrary requests, via an institutional repository or you may need to contact the author directly. Get in touch with us on the chat box below if you and we can help with locating sources.

How to evaluate content?

Take the same approach you would to evaluate any content you find online. Unlike commercially published sources, grey literature does not go through the same level of scrutiny as an article in a peer-reviewed journal would.

The questions you can use to evaluate sources are:


Who is the author(s) What are their credentials? Are they an expert in their field? (use Google Scholar as quick check to see if they’ve been cited by others) If there isn’t an author then look at the organisations “mission statement” or “about us” page to access their impartiality.


What information is being given? Is it opinion, commentary, or factual? Does the item have a detailed reference list or bibliography?


Where is the information coming from? Check the website domain. Secure websites often begin with https://

Remember that links for grey literature, unless found in an institutional repository, may not be maintained, so when you find it, save it. – UK commercial and general – UK academic institutions (Universities, Colleges, Research establishments) - UK government (including local)

.edu – U.S. educational institutions such as Universities

.org –organisations (often non-profit but not always


When was the information written or published – is it up-to-date? (Sources with no date information should be treated with caution) When was the website last updated? Check the bibliography for relevant contemporary material?


Is the text well-written? Are their spelling or grammatical errors? Is the language emotive? Does the work seem to be balanced in presentation? Is the author’s standpoint clear? Are any limits clearly stated? Is it clear where the data came from? A useful article and checklist can be found here.

Using Search Engines: Search Tips for improving results

You can also use search engines effectively to search for Grey Literature. Try using Google Advanced search or DuckDuckGo

New Projects

If you are starting a new research project then try clearing your browsing data before you start to avoid your previous searches influences your results. Not only will this help you get to the results you want, but will help reduce the effects of the filter bubble. Also worth logging out of user accounts; try incognito mode; not 100% effective.


It's important to remember that most search engines will automatically look for synonyms and variations of your keywords and will exclude results if there are too few results. This is a helpful aspect of search engines, however, you are unable to control the searches, making them not reproducible by others.

Search Commands

Use search commands, filters or advanced search functions to get back the results you want and avoid information overload. Search command AND is often assumed. (See the Search Commands tab for details).

  Google DuckDuckGo
Phrase Search "development policy" "development policy"
Boolean OR (AND assumed) ANDOR. Tip use () to group your OR searches
Exclude Put - before the word. For example, animal -dog Put or NOT before the word. For example, animal -dog / animal NOT dog
Wild Card Automatic Automatic
Truncation Automatic Automatic
Proximity Use asterisk in place of missing word. E.g., robot * sensor -
Date Range .. e.g., 2001..2015 or use filters  Use filters
File type filetype: find files in specific format. E.g., filetype:pdf filetype: find files in specific format. E.g., filetype:pdf
Site/Domain Site: search specific pages or domains. E.g., / Site: search specific pages or domains. E.g., /
title search intitle: search for word in title of page. E.g., intitle:development intitle: search for word in title of page. E.g., intitle:development

Public Health: Clinical

Name Contents
Grey Literature Report Indexes publications in health services
Cochrane Library Database of Medical Systematic Reviews
National Institute for Health and Care Excellence (NICE) Clinical guidance, systematic reviews, evidence and research recommendations relating to health, drugs and technologies, public health, social care and healthcare management and commissioning
PubMed Indexes biomedical literature from MEDLINE, life science journals, and online books. Includes Clinical Trials, systemic reviews, technical reports, government documents.
NICE evidence Search Google-style interface to a comprehensive evidence base for anyone in health and social care who takes decisions about treatments or the use of resources. Provides a portal to a variety of online resources.
North Grey Literature Collection A grey literature collection relating to health and public health in the North of England. Includes lists of resources and keywords for finding grey literature.
Open Grey A Grey literature information from Europe. Provides access to 700,000 bibliographical references. A resource that provides information on publicly and privately supported clinical studies; maintained by the National Library of Medicine (NLM) at the National Institutes of Health (NIH).

More information available at on the Medicine Subject Guide and Grey Literature Report. You can search for sources using Google Advanced search.

Public Health: Social Work

Social Care Online (SCIE) UK: Social care information. Includes research briefings, reports, government documents, journal articles, and websites
Department of Health & Social Care Find guidance and regulation information for Health and Social care

Theses and Dissertations

Name Coverage
EThOS  UK: Doctoral theses
Sussex Research Online University of Sussex: Doctoral Theses
Proquest Dissertations and Theses: Open mainly US: Open access Dissertations and Doctoral Theses
Open Access Thesis and Dissertations International: Post-graduate Dissertations and Doctoral Thesis
PsycINFO International: Psychology Dissertations and Doctoral Theses
Library Hub Discover UK & Ireland: Dissertations and Doctoral Theses

Google Scholar can be a useful tool to identify potential resources. Full information available on Thesis and Dissertation subject guide

Conference Proceedings

Database Subject
Web of Science Science, Social Science
Scopus Science, Social Science
PsycINFO Psychology
Medline Medicine

On the above databases, go to the filter settings and limit by Proceedings.


Name Subject
PsyArXiv Psychology
Sussex Research Online All
OpenDOAR All
bioRxiv Biology, genomics, biochemistry, bioinformatics, biophysics, life sciences
PeerJ Preprints Biology, Medicine, computer science

More information on available pre-print servers available here. There are also many Institutional Repositories.