APA Format
World Health Organization
. (1990,1991;1993). International travel and health : vaccination requirements and health advice situation as on 1 January 1993. Geneva : WHO
MLA Format
World Health Organization
. International travel and health : vaccination requirements and health advice situation as on 1 January 1993. Geneva : WHO, 1990,1991;1993
Australian/Harvard Format
World Health Organization
. 1990,1991;1993. International travel and health : vaccination requirements and health advice situation as on 1 January 1993. WHO, Geneva
Warning: These citations may not always be 100% accurate.