Grey Literature is defined as "information produced on all levels of government, academia, business and industry in electronic and print formats not controlled by commercial publishing." ICGL Luxembourg definition, 1997, expanded in NY, 2004.
Examples:
Theses and dissertations
Census, economic and other "grey" data sources
Conference proceedings, poster presentations and abstracts
This three-part Web conference series provided an overview of grey literature and approaches to searching the grey literature for health services research; a consumer's guide to conducting advanced searches of grey literature; and a producer's perspective on the "searchability" of grey literature and how to effectively produce and distribute research.