Grey literature is information produced outside of traditional publishing and distribution channels, and can include reports, policy literature, working papers, newsletters, government documents, speeches, white papers, urban plans, and so on.
This information is often produced by organizations "on the ground" (such as government and inter-governmental agencies, non-governmental organizations, and industry) to store information and report on activities, either for their own use or wider sharing and distribution, and without the delays and restrictions of commercial and academic publishing. For that reason, grey literature can be more current than literature in scholarly journals.
However, because grey literature (usually) does not go through a peer review process, the quality can vary and should be closely evaluated. Be sure to evaluate your source.
A source for working papers and grey literature in business, economics, and law provided by the Library of Congress. Most are links to Central Banks and Think Tanks’ working papers, all in one place for convenience.
This site is a free, large searchable database of economics working papers, many of which are viewable or downloadable. Also cites articles and book chapters. Uses the complete RePEc database, which includes bibliographic data contributed by over 350 worldwide archives.
References to literature of international economics, development, and finance, from the catalog of the World Bank-International Monetary Fund Library. Includes books, journal articles (1980-present), working papers, conferences, technical reports.