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