1. Department of Otolaryngology-Head and Neck Surgery; Johns Hopkins University School of Medicine; Baltimore Maryland U.S.A.
2. Department of Otolaryngology-Head and Neck Surgery; Ohio State University School of Medicine; Columbus Ohio U.S.A.
3. Department of Otolaryngology-Head and Neck Surgery; Children's National Medical Center; George Washington University, School of Medicine; Washington DC U.S.A.
4. Johns Hopkins University School of Public Health; Baltimore Maryland U.S.A.