Grey literature refers to both published and unpublished research material that is not available commercially. It can be the best source of up-to-date research on some topics. e.g Statistics relating to Australian health. Note however that grey literature is usually not subject to peer review and must be evaluated accordingly. Grey literature can be found by searching the internet, databases, institutional repositories and catalogues.
Grey literature consists of:
Alberani, V., De Castro Pietrangeli, P. & Mazza, A.M. (1990). The use of grey literature in health sciences: A preliminary survey. Bulletin of the Medical Library Association, 78 (4) : 358-363. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC225438/
A checklist for evaluating grey literature has been developed by Jess Tyndall, Flinders University.
It uses AACODS (Authority, Accuracy, Coverage, Objectivity, Date and Significance) to evaluate grey literature materials.
For a full version of this checklist please see this document.
In addition to the sources listed above, internet searching can locate other useful sources: