1. Department of Biostatistics and Epidemiology, Center for Clinical Epidemiology and Biostatistics; University of Pennsylvania, Perelman School of Medicine; Philadelphia PA
2. Department of Otorhinolaryngology-Head and Neck Surgery; University of Pennsylvania, Perelman School of Medicine; Philadelphia PA
3. Department of Surgery; University of Arizona; Tucson AZ
4. Philadelphia Veterans Affairs Medical Center; Philadelphia PA