APA Format
World Health Organization (WHO) . (). The selection of assential drugs, TRS.641. : Geneva WHO 1979
MLA Format
World Health Organization (WHO) . The selection of assential drugs, TRS.641. : Geneva WHO 1979,
Australian/Harvard Format
World Health Organization (WHO) . . The selection of assential drugs, TRS.641. Geneva WHO 1979, 
Warning: These citations may not always be 100% accurate.