1. John Radcliffe Hospital; c/o Cochrane ENT DIsorders Group, ENT Dept, West Wing; Headley Way Oxford Oxon UK OX3 9DU
2. De La Salle University, Health Sciences Campus; Clinical Epidemiology Unit; Cong. Road Dasmariñas Cavite 4114 Philippines
3. University of Liverpool; Centre for Medical Statistics and Health Evaluation; Shelley's Cottage Brownlow Street Liverpool UK L69 3GS