1. Department of Otorhinolaryngology-Head and Neck Surgery, Chungbuk National University College of Medicine, Chungbuk National University Hospital, Cheongju, Korea.
2. Center of Morphological Experiment, Medical College of Yanbian University, Yanji, China.
3. Department of Otorhinolaryngology-Head and Neck Surgery, Chuncheon Sacred Heart Hospital and Institute of New Frontier Research, Hallym University College of Medicine, Chuncheon, Korea.
4. Department of Otorhinolaryngology-Head and Neck Surgery, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.