1. Duke Voice Care Center, Division of Otolaryngology–Head & Neck SurgeryDuke University Medical CenterDurham North Carolina U.S.A.
2. Division of Public Health & Study Design and Biostatistics CenterUniversity of UtahSalt Lake City Utah U.S.A.
3. University of UtahSalt Lake City Utah U.S.A.
4. Department of Otolaryngology–Head & Neck SurgeryUniversity of California, San FranciscoSan Francisco California U.S.A.