1. Department of Otorhinolaryngology; Head and Neck Surgery; Berlin Institute of Health; Charité - Universitätsmedizin Berlin; corporate member of Freie Universität Berlin; Humboldt-Universität zu Berlin; Campus Benjamin Franklin; Berlin Germany
2. Department of Otorhinolaryngology; Mayo Clinic; Rochester MN USA
3. Center of Otorhinolaryngology Rhein-Neckar; Mannheim Germany
4. Department of ENT-FPS; University Medical Center Utrecht; Utrecht The Netherlands