Gray/Grey Literature

I learned a new term today. It appears I have been using gray or grey literature without knowing it. I came across the term because somebody recently complemented me on my use of such sources. This prompted me to look the term up. Brian S. Matthews defines gray literature as "documentary material that is not commercially published and is typically composed of technical reports, working papers, business documents, and conference proceedings." A quick Google search in fact shows that there is a large body of literature regarding the use of gray literature. A search for "gray literature" turned up 74,100 hits and one for "grey literature" got around 168,000 hits. Because gray literature has historically been poorly indexed and catalogued as well as difficult to obtain, finding it and using it presents unique problems. Despite these problems I would say that there is a lot of valuable material available to scholars in gray literature. From my brief Internet search on the topic it appears that the scientific and technical fields are considerably more advanced in their use of gray literature than the social sciences. The humanities including history in turn are woefully behind the social sciences in their exploitation of gray literature.