* "PPNG first appeared in the Philippines among a sexually active core group of prostitutes and servicemen in and around U.S. military bases where many women habitually took black market penicillin as a prophylactic treatment ..."<ref name=war /> | * "PPNG first appeared in the Philippines among a sexually active core group of prostitutes and servicemen in and around U.S. military bases where many women habitually took black market penicillin as a prophylactic treatment ..."<ref name=war /> |