1. Ear-Nose-Throat Clinic; Carl Thiem Hospital; Cottbus Germany
2. Institute for Medical Biometry, Epidemiology, and Informatics; Medical Center of the University of Mainz; Mainz Germany
3. Medical School, Aristotle University of Thessaloniki; Thessaloniki Greece
4. Department of Otorhinolaryngology; Medical Center of the University of Mainz; Mainz Germany