1. Polio and Polio Vaccine; Epidemiology and Prevention of Vaccine-Preventable Diseases National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention. 〈http://www.cdc.gov/vaccines〉; 2012
2. Polio Disease In-Short Centers for Disease Control. 〈http://www.cdc.gov/vaccines/vpd-vac/polio/in-short-both〉; accessed 07.16.13.
3. Poliomyelitis Fact Sheet No 114 World Health Organization. 〈http://www.who.int/mediacentre/factsheets/fs114/en/〉; 2013 accessed 07.16.13.
4. Sanchez L. Polio virus discovered in Cairo Jan 22, 2013. Daily News Egypt. 〈http://www.dailynewsegypt.com/2013/01/22/polio-virus-discovered-in-cairo/〉; accessed 07.16.13.
5. Sterman A. More polio virus traces detected in Israel June 12, 2013. Times of Israel. 〈http://www.timesofisrael.com/more-polio-virus-traces-detected-in-israel/〉; accessed 07.16.13.