Grey Literature refers to publications issued by government, academia, business, and industry, in both print and electronic formats, but not controlled by commercial publishing interests, and where publishing is not the primary business activity of the organization. Scientific grey literature comprises newsletters, reports, working papers, theses, government documents, bulletins, fact sheets, conference proceedings and other publications distributed free, available by subscription, or for sale. The quest for scientific knowledge is an evolutionary process in which every increment of new knowledge adds to, modifies, refines, or refutes earlier findings (Subramanyan, 1981). Scholarly, peer reviewed journals are the major venue of communication for the science community to publish and present results of current research to colleagues. Since research tends to focus on specific areas of a discipline, readers often desire additional information to help place the research in a wider perspective. Auger (1989) pointed out that the advantages of grey literature over other means of dissemination are quick access, greater flexibility, and the opportunity to go into considerable detail when necessary. Thus, grey literature, covering nearly every aspect of the sciences, serves scholars and lay readers alike with research summaries, facts, statistics, and other data that offer a more comprehensive view of the topic of interest.

http://library.brooklyn.cuny.edu/access/greyliter.htm