Difficulties in polio eradication.
O
O
Razum
J
J
Liyanage
K R
KR
Nayar
D003906:Developing Countries; D006801:Humans; D017589:Immunization Programs; D007194:India; D007812:Laos; D011051:Poliomyelitis / Q000517:prevention & control*; D023321:Poliovirus Vaccines / Q000008:administration & dosage*
D023321:Poliovirus Vaccines