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SR resources for Librarians: Grey Literature

What's Grey Literature?

Grey literature is literature that is not usually published in journals and monographs or indexed in commercial databases and catalogues. It consists of:

  • preprints

  • hard to find studies;

  • reports, or dissertations, conference abstracts or conference papers;

  • governmental or private sector research;

  • clinical trials - ongoing or unpublished and experts and researchers in the field

  • communication with experts in the subject area


These sources can yield information not found in the published databases. Searching the grey literature is done by both the librarian and individuals from the review team. Steps in the grey literature search:

  1. Discuss the grey literature search sources to be searched

  2. Agree on how search will be executed, the keywords and phrases that will be searched:

  3. Identifying the resources the librarian will search

  4. Identify the resources to be searched by the clients

  5. Agree on timeline for search

  6. Execute the search

  7. Review results


Grey Lit resources


U of M Library toolkits may include links to grey literature on that subject. CADTH also has a helpful checklist to use when searching the grey literature, Grey Matters: A practical search tool for evidence-based medicine. Other sources of grey literature include:


Clinical Trial Registries

*Information and links on this page came from the NIH Systematic Review Library Guide 

PrePrint Sources


Documenting Grey Lit Searches


Aspects of your search to report include the following:

  • Exact search strategies, including which terms in which search engines

  • Every website searched, which pages were browsed on that website, and which search terms were used

  • Date searches were conducted

  • Resources identified from grey literature searching should be accurately tagged in the reference managing software being used

  • Type of resource retrieved from search (e.g. report, journal article, presentation, book, etc.)

  • Number of resources identified from each website/source

  • Number of resources identified from grey literature searching