1. Department of Otorhinolaryngology - Head and Neck Surgery, University of Helsinki, Helsinki University Hospital
2. Department of Otorhinolaryngology-Head and Neck Surgery, Turku University Hospital, University of Turku
3. Department of Otorhinolaryngology - Head and Neck Surgery, Tampere University Hospital, University of Tampere
4. Department of Otorhinolaryngology - Head and Neck Surgery, Kuopio University Hospital, University of Eastern Finland
5. Department of Otorhinolaryngology - Head and Neck Surgery, Oulu University Hospital, University of Oulu
6. Department of Oral and Maxillofacial Surgery, University of Helsinki, Helsinki University Hospital
7. Research Program Unit, Faculty of Medicine, University of Helsinki
8. Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki