The standard definition of grey literature is information produced on all levels of government, academics, business and industry in electronic and print formats not controlled by commercial publishing, i.e. when publishing is not the primary activity of the producing body. Because grey literature isn't published commercially, it can be challenging to track down. Fortunately, the internet has made grey literature much more accessible to use and locate. This guide will introduce you to grey literature and provide some resources on conducting a grey literature research.
Farace, D and Schöpfel, J. (2010) Grey Literature in library and information science. Walter de Gruyter GmbH & Co. KG, Berlin/New York.