1. Ad Hoc Committee on Service Delivery in the Schools. American Speech-Language-Hearing Association;Definitions of communication disorders and variations;ASHA Suppl,1993
2. National Institute of Deafness and Other Communication Disorders http://www.nidcd.nih.gov/health/voice/vocalabuse.html 2011
3. National Institute on Deafness and Other Communication Disorders http://www.nidcd.nih.gov/about/learn/mission.html
4. Populations in the U.S. workforce who rely on voice as a primary tool of trade: A preliminary report;Titze;J Voice,1997
5. Snyder TD Dillow SA Digest of Education Statistics 2010 2011