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