[1] University of Helsinki and Helsinki University Hospital,Department of Otorhinolaryngology
[2] University of Tampere and Tampere University Hospital,Head and Neck Surgery
[3] University of Turku and Turku University Hospital,Department of Otorhinolaryngology
[4] University of Oulu and Oulu University Hospital,Head and Neck Surgery
[5] University of Eastern Finland and Kuopio University Hospital,Department of Otorhinolaryngology
[6] University of Helsinki and Helsinki University Hospital,Head and Neck Surgery
[7] University of Turku,Department of Otorhinolaryngology