Grey Literature

As quoted by the Grey Literature International Steering Committee (GLISC) (see page 1), grey literature has been defined as:
 
Information produced on all levels of government, academics, business and industry in electronic and print formats not controlled by commercial publishing i.e. where publishing is not the primary activity of the producing body.

In other words, the work is not tied to or controlled by commercial publishers (like the companies that publish your textbooks), who seek profit on the research or information produced.  Grey literature is self-published and typically comes from:

• Government agencies
• Research institutes
• Organizations or companies
• Associations

1. Evaluate what you find - Because grey literature does not go through the same peer review process of something published commercially, caution needs to be taken when selecting grey literature to use.  As with any resource, even formally published ones, bias or inaccuracies can exist and it is important to have some understanding of the author/originator of the information and their stance on a particular topic or issue. 
2. Issues around longevity - Resources openly available on the Internet can sometimes vanish, particularly if they are older items or if the website is not being kept up.  If you find something useful, grab it!  Typically things found in a repository or database have more longevity, but for one-off items posted on a website, that is not always the case.