1. Institute of Medical Sociology, Medical Faculty, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
2. Department of Otolaryngology, Head and Neck Surgery, University of Leipzig, Leipzig, Germany
3. Department of Otorhinolaryngology, Jena University Hospital, Jena, Germany
4. Department of Otorhinolaryngology, Clinical Center Dresden-Friedrichstadt, Dresden, Germany
5. Department of Otorhinolaryngology, Helios-Klinikum, Erfurt, Germany
6. Department of Otorhinolaryngology, Hospital Chemnitz, Chemnitz, Germany
7. Department of Otorhinolaryngology, Hospital Martha–Maria, Halle–Dölau, Germany
8. Department of Otolaryngology, Head and Neck Surgery, St. Georg Hospital, Leipzig, Germany
9. Department of Otolaryngology, Head Neck Surgery, Elbland-Hospital, Riesa, Germany
10. Department of Otolaryngology, Head Neck Surgery, Südharz-Hospital, Nordhausen, Germany
11. Department of Otorhinolaryngology/Plastic Surgery, SRH Wald-Klinikum Gera, Gera, Germany
12. Department of Otorhinolaryngology, Head & Neck Surgery, University Medicine Halle, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
13. Department of Otorhinolaryngology, Head and Neck Surgery, Carl Thiem Klinikum, Cottbus, Germany
14. Institute of Medical Biostatistics, Epidemiology and Informatics (IMBEI), University Medical Centre of Johannes Gutenberg University Mainz, Mainz, Germany