Não informado. (1973). WHO Offset Publication. World Health Organization.
Chicago (17e ed.) BronvermeldingNão informado. WHO Offset Publication. Geneva, Suíça: World Health Organization, 1973.
MLA (8e ed.) BronvermeldingNão informado. WHO Offset Publication. World Health Organization, 1973.
Let op: Deze citaties zijn niet altijd 100% accuraat.