1. Department of Otorhinolaryngology, Juntendo University School of Medicine, Tokyo
2. Department of Otorhinolaryngology, Iwaki General Hospital, Iwaki
3. Department of Otorhinolaryngology, Teikyo University School of Medicine, Tokyo
4. Department of Otorhinolaryngology, University of Occupational and Environmental Health, School of Medicine, Kitakyushu
5. Department of Otorhinolaryngology, Koseinennkin General Hospital, Sendai, Japan