Wikipedia Unobtrusive Measures. (n.d.). Retrieved December 5, 2008 from http://en.wikipedia.org/wiki/Unobtrusive_measures
Wiley, David (2008). OER Handbook for Educators Version 1.0. WikiEducator.org. Retrieved December 5, 2008 from http://www.wikieducator.org/OER_Handbook/educator_version_one.
Effective Business and Professional Writing: From Problem to Proposal, second edition. (Magrino and Goeller)
The Business Writer's Companion, seventh edition (Alred, Brusaw and Oliu)