Grey literature is “information produced by all levels of government, academics, business and industry in electronic and print formats not controlled by commercial publishing”. (GreyNet)
Grey literature includes:
Theses and dissertations, conference proceedings, newsletters, reports, government documents, informal communications, translations, census data, research reports, technical reports, standards, patents, videos, clinical trials and practice guidelines, eprints, preprints, wiki articles, emails, blogs, listserv archives, repository content.
Grey literature may present a number of challenges for the researcher: