Grey literature is material that is not commercially published. It can come in the form of conference proceedings, technical reports, working papers, preprints, as well as blogs or podcasts. Because grey literature hasn't been published it can be challenging to locate.

There are three basic ways to search for Grey Literature:

• Search or browse organizational websites (such as WHO, NIH, Robert Wood Johnson Foundation, Kaiser Family Foundation, Pew Charitable Trusts, etc.). Organizations produce reports, statistics, and other unpublished resources. Search sites individually and/or browse areas such as "publications" or "statistics."
• Search websites that index unpublished material such as the following:

OpenGrey - an open access database of European grey lit containing over 700,000 references. Can limit by year or institution, includes save and export functionality. Coverage: 1980-2020; ceased.

The New York Academy of Medicine Grey Literature Report - from 1999-2016, a bimonthly publication of The New York Academy of Medicine Library alerting readers to new grey literature publications in health services research and selected public health topics. In addition to this alert service, all resources are added and indexed in their Online Catalog. No longer maintained, but content is still available.

HSRProj (Health Services Research Projects in Progress - From the National Library of Medicine, a database providing access to ongoing grants and contracts in health sciences research.

OpenDOAR - in addition to providing a list of open access repositories, OpenDOAR lets you search repository contents.

• Use a search engine such as Google. Google is considered the "go-to" search engine, but you should try others too. A list of alternatives can be found here; see in particular the list of medical search engines. You can easily limit your Google searches to specific documents by adding:
  • keywords -- for example, guidelines OR protocols
  • document types -- for example, filetype:pdf
  • limit by source -- for example, site:.gov, site:.edu  

Additional Grey Lit resources:

GreyNet International - A selection of web-based resources in grey literature

Mednar - does a "deep web" search. Limit results by selecting "topics" on left side.

Nursing Times - Great article on searching for grey literature.

OpenSIGLE - System for information on grey literature in Europe.

Health and Medicine Division (HMD) of the National Academies of Sciences, Engineering, and Medicine - contains reports and publications that provide objective and straightforward advice to decision makers and the public.

Conference proceedings can be a valuable source of current research but they're often difficult to find. You can often find posters, presentations, and meeting abstracts in institutional repositories. Try searching Google Scholar for these. Another wonderful resource for meeting abstracts is the GVSU database Web of Science. You can search various fields, including conference name.