1. http://www.who.int/wer/2014/wer8909.pdf
2. Disease eradication as a public health strategy: a case study of poliomyelitis eradication;Aylward;Bull World Health Organ,2000
3. http://101.96.8.165/www.who.int/biologicals/IPV_FINAL_for_BS2233_07072014(2).pdf