1. Epidemiology and Statistics Program, Division of Scientific Programs; The University of Utah; Salt Lake City Utah
2. National Institute on Deafness and Other Communication Disorders, Bethesda, Maryland; Department of Communication Sciences and Disorders, and Division of Otolaryngology-Head and Neck Surgery (Adjunct); The University of Utah; Salt Lake City Utah
3. Duke Voice Care Center, Division of Head and Neck Surgery and Communication Sciences; Duke University Medical Center; Durham North Carolina U.S.A