1. Department of Otorhinolaryngology ‐ Head and Neck Surgery Keio University School of Medicine Shinjuku Tokyo Japan
2. Department of Otorhinolaryngology ‐ Head and Neck Surgery Kawasaki Municipal Kawasaki Hospital Kawasaki Kanagawa Japan
3. Department of Otorhinolaryngology Saiseikai Utsunomiya Hospital Utsunomiya Tochigi Japan
4. Department of Otorhinolaryngology Saiseikai Yokohamashi Nanbu Hospital Yokohama Kanagawa Japan
5. Department of Otorhinolaryngology Yokohama Municipal Citizen's Hospital Yokohama Kanagawa Japan
6. Department of Otorhinolaryngology Kyosai Tachikawa Hospital Tachikawa Tokyo Japan
7. Department of Otorhinolaryngology Saiseikai Yokohamashi Tobu Hospital Yokohama Kanagawa Japan
8. Department of Otorhinolaryngology Tokyo Saiseikai Central Hospital Minato Tokyo Japan