1 Departement of Otorhinolaryngology - Head Neck Surgery, Faculty of Medicine Universitas Airlangga, Mayjen Prof. Dr. Moestopo Street No. 47, Pacar Kembang, Tambaksari, Jawa Timur Surabaya, 60132 Indonesia.
2 Departement of Public Health and Preventive Medicine, Faculty of Medicine Universitas Airlangga, Mayjen Prof. Dr. Moestopo Street No. 47, Pacar Kembang, Tambaksari, Surabaya, 60132 Indonesia.
3 International Centre for Evidence in Disability, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT UK.