1. Department of Otorhinolaryngology, Head and Neck SurgeryUniversity of CologneCologne Germany
2. Department of Otorhinolaryngology, Head and Neck SurgeryJena University HospitalJena Germany
3. Department of Otorhinolaryngology, Head and Neck SurgeryUniversity of GiessenGiessen Germany
4. Department of Otorhinolaryngology, Head and Neck SurgerySt. Anna ClinicWuppertal Germany