"The Fourth International Conference on Grey Literature (GL '99) in Washington, DC, in October 1999 defined grey literature as follows: "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." From the New York Academy of Medicine Grey Literature Report (http://www.greylit.org/about)
"Grey Literature" includes reports, presentations, technical manuals and other materials produced by a range of stakeholders. These materials can be difficult to find. In addition to the resources listed below, you may also want to review the resources listed under Policy Resources (especially PAIS and PolicyFile) as well as under Federal Reports.