Grey literature is 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" (Fourth International Conference on Grey Literature, Washington D.C., 1999). Grey literature includes resources that fall outside of what is traditionally considered 'research' material, including: reports, theses, statistical collections, conference proceedings, bibliographies, technical and market research reports, and so on. These materials are often not found in libraries and academic databases.
This is a list of online white paper collections prepared by United States Government Agencies.