1. Program in Epidemiology, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
2. Department of Head and Neck Surgery, The Affiliated Cancer Hospital of Zhengzhou University, Zhengzhou, Henan, P.R.China
3. Department of Epidemiology, University of Washington, Seattle, Washington, USA
4. Department of Otolaryngology, Head and Neck Surgery, University of Washington, Seattle, Washington, USA