APA
World Health Organization, . (1998). International travel and health : vaccination requirements and health advice : situation as on 1 January 1998. WHO, Geneva: .
Chicago
World Health Organization, . 1998. International travel and health : vaccination requirements and health advice : situation as on 1 January 1998. WHO, Geneva: .
Harvard
World Health Organization, . (1998). International travel and health : vaccination requirements and health advice : situation as on 1 January 1998. WHO, Geneva: .
MLA
World Health Organization, . International travel and health : vaccination requirements and health advice : situation as on 1 January 1998. WHO, Geneva: . 1998.