1. Department of Otorhinolaryngology-Head and Neck Surgery, Kyung Hee University Hospital, Kyung Hee University College of Medicine, Seoul, Korea.
2. Department of Otorhinolaryngology-Head and Neck Surgery, Dongguk University Ilsan Hospital, Goyang, Korea.
3. Department of Otolaryngology-Head and Neck Surgery, Chonnam National University Hospital and Chonnam National University Medical School, Gwangju, Korea.
4. Department of Otolaryngology-Head and Neck Surgery, Gil Medical Center, Gachon University College of Medicine, Incheon, Korea.
5. Department of Otorhinolaryngology, Gyeongsang National University Hospital and Gyeongsang National University School of Medicine, Jinju, Korea.
6. Department of Otorhinolaryngology, Pusan National University Yangsan Hospital, Busan, Korea.
7. Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
8. Department of Otorhinolaryngology-Head and Neck Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
9. Departments of Otorhinolaryngology-Head and Neck Surgery, Sanggye Paik Hospital, College of Medicine, Inje University, Seoul, Korea.
10. Kimyounghyo ENT Clinic, Incheon, Korea.
11. Department of Otorhinolaryngology-Head and Neck Surgery, Chungnam National University School of Medicine, Daejeon, Korea.
12. Department of Otorhinolaryngology-Head and Neck Surgery, Chuncheon Sacred Heart Hospital, Hallym University College of Medicine, Chuncheon, Korea.
13. Department of Otorhinolaryngology-Head and Neck Surgery, Chonnam National University Hwasun Hospital, Chonnam, Korea.
14. Department of Otorhinolaryngology-Head and Neck Surgery, School of Medicine, Kyungpook National University, Daegu, Korea.
15. Department of Otorhinolaryngology-Head and Neck Surgery, Konyang University College of Medicine, Daejeon, Korea.
16. Department of Otorhinolaryngology-Head and Neck Surgery, National Medical Center, Seoul, Korea.
17. Department of Preventive Medicine, Seoul National University College of Medicine, Seoul, Korea.
18. Department of Otorhinolaryngology, Dankook University College of Medicine, Cheonan, Korea.
19. Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Daegu Catholic University, Daegu, Korea.
20. Department of Otorhinolaryngology-Head and Neck Surgery, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, Seoul National University College of Medicine, Seoul, Korea.