1. United States Centers for Disease Control and Prevention. Diphtheria. In: Atkinson W Wolfe S Hamborsky J (eds). Epidemiology and Prevention of Vaccine-Preventable Diseases, 12th edn. Washington, DC: Public Health Foundation, 2012, 75–86.
2. World Health Organization. Diptheria Reported Cases. http://apps.who.int/immunization_monitoring/globalsummary/timeseries/tsincidencediphtheria.html (13 February 2014, date last accessed).
3. United States Centers for Disease Control and Prevention. Tetanus. In: Atkinson W Wolfe S Hamborsky J (eds). Epidemiology and Prevention of Vaccine-Preventable Diseases, 12th edn. Washington, DC: Public Health Foundation, 2012, 291–300.
4. World Health Organization. Tetanus (Total) Reported Cases. http://apps.who.int/immunization_monitoring/globalsummary/timeseries/tsincidencettetanus.html (13 February 2014, date last accessed).
5. Goh KT (ed). The national childhood immunisation programme. In: Epidemiological Surveillance of Communicable Diseases in Singapore. Tokyo: Southeast Asian Medical Information Center, 1983, 245–71.