1. First Department of Otorhinolaryngology Head and Neck Surgery, Metropolitan General, 15562 Athens, Greece
2. First Department of Otorhinolaryngology, Hippocrateion General Hospital, 11527 Athens, Greece
3. Laboratory of Hygiene, Social & Preventive Medicine and Medical Statistics, School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
4. Second Department of Urology, Aristotle University of Thessaloniki, General Hospital ‘Papageorgiou’, 56403 Thessaloniki, Greece