Skip to Main Content

Grey Literature: What is grey literature and why use it?

What is grey literature?

The Fourth International Conference on Grey Literature (GL '99) in Washington, DC, in October 1999 defined grey literature as: "That which is produced on all levels of government, academics, business and industry in print and electronic formats, but which is not controlled by commercial publishers."

Grey literature is research which is either unpublished or published through channels other than commercial publishing. Most of it is not found in bibliographic databases. You should consider what type of literature you are interested in before you begin searching. Not all grey literature is relevant to all researchers and it will depend on the subject studied (clinical trials will not be relevant to research about the environment for example but research reports may well be relevant). 

Types of grey literature

Types of grey literature  Creators of grey literature 
Article pre-prints and post prints Interviews Press releases
Annual reports Lectures and lecture notes Research reports
Blogs Legislation Social networking platforms
Bulletins Maps Speeches
Clinical trials  Market reports Standards
Company information News  Statistics and statistical reports
Conference papers or proceedings Newsletters or newspapers Surveys
Course materials Pamphlets Theses
Discussion forums Patents Tweets
Dissertations Personal communication Unpublished manuscripts
E-mails and e-mail discussion lists Photographs Video sharing sites
Factsheets Policy statements or briefs Wikis
Geological and geophysical surveys Posters White papers
Government documents and reports   Working papers
  • Government agencies
  • Research institutes
  • Academics
  • Researchers
  • Companies
  • Organisations
  • Associations
  • Campaign and pressure groups
  • NGOs


Why include grey literature in your research?

Why should you use grey literature?

  • It can record findings in niche or emerging research areas not found elsewhere
  • To provide a comprehensive, balanced and unbiased picture of the research on a particular topic – negative results are more often included in grey literature so including unpublished material is a way of counteracting positive bias
  • It can be more current than mainstream published literature and its findings may not find their way through into journals or books until years later after passing through lengthy peer review and editorial processes
  • It can be more detailed than the literature published through commercial channels
  • It can be a good source of raw data
  • Enables the viewpoints of individuals less likely to publish in journals to be heard
  • Provides valuable insight of a sector or industry perspective 

Evaluating grey literature

Although grey literature can be very valuable and useful for your projects, it has often been through less thorough processes of reviewing and quality assurance. It is therefore crucial to carefully consider whether the grey literature you are using is trustworthy, reliable and accurate.

One tool you can use to help with evaluating grey literature is the AACODS Checklist for appraising grey literature


Based on University of Wolverhampton, University of Exeter and University College Cork guides to grey literature