Gray Literature as Prior Art?

Brian S. Mathews writes for College and Research Library News in March 2004 that "gray literature" is commonly defined as any documentary material that is not commercially published and is typically composed of technical reports, working papers, business documents, and conference proceedings. However, much of this gray literature is now freely available on many Web sites, and is selectively indexed by numerous commercial database vendors. His paper provides a list of Web sites that aid in understanding the nature of gray literature as well as various search tools. While the majority of his selections concentrate upon scientific and technical literature, other resources have been included to illustrate the wide range and variation of gray literature.