Gray literature is literature that has been published, but the publishing process did not go through traditional commercial publishing pathway.
Professional organizations, government departments & agencies, and others such as the Pew Research Center and AARP publish their own resources. These works are considered "gray."
Gray Literature
Hopewell S, Loudon K, Clarke Mike J, Oxman Andrew D, Dickersin K. Publication bias in clinical trials due to statistical significance or direction of trial results.
Cochrane Database of Systematic Reviews [serial on the Internet]. 2009; (1): MR000006. http://www.ncbi.nlm.nih.gov/pubmed/19160345
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Locate books, journals and magazines, music scores, archival materials, and media in libraries worldwide.
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General Gray Literature Resources
Reports
Dissertations and Theses
Dissertations and theses in all subject areas from universities around the world.
NOTE: Universities archive dissertations written by their students. Search individual university library catalogs.