1. Department of Otolaryngology-Head and Neck Surgery, Seoul National University College of Medicine, Seoul, Korea
2. Department of Otolaryngology-Head and Neck Surgery, Sungkyunkwan University School of Medicine, Seoul, Korea
3. Department of Otolaryngology-Head and Neck Surgery, University of Ulsan, College of Medicine, Seoul, Korea
4. Department of Otolaryngology-Head and Neck Surgery, Kosin University College of Medicine, Busan, Korea
5. Department of Otolaryngology-Head and Neck Surgery, Dankook University, Medical College, Cheonan, Korea