1. Department of Otolaryngology; Hospital Universitario Central de Asturias; Oviedo Spain
2. Instituto Universitario de Oncología del Principado de Asturias; Oviedo Spain
3. Department of Otolaryngology-Head and Neck Surgery; Radboud University Nijmegen Medical Center; Nijmegen The Netherlands
4. Departments of Surgery and Otolaryngology-Head and Neck Surgery; Albert Einstein College of Medicine; Montefiore Medical Center; Bronx New York
5. Division of Gastroenterology; S. Antonio Hospital; Padua Italy
6. ENT Clinic; University of Udine; Udine Italy
7. Department of Otolaryngology-Head and Neck Surgery; Mayo Clinic; Phoenix Arizona