Do oral contraceptives improve vocal quality? Limited trial on low-dose formulations. - Amir O; Biron-Shental T; Muchnik C; Kishon-Rabin L; Amir, Ofer; Biron-Shental, Tal; Muchnik, Chava; Kishon-Rabin, Liat (Obstetrics & Gynecology, 2003)