APA
WHO, . (1999). International travel and health : vaccination requirements and health advice : situation as on 1 January 1999. auth., Geneva: .
Chicago
WHO, . 1999. International travel and health : vaccination requirements and health advice : situation as on 1 January 1999. auth., Geneva: .
Harvard
WHO, . (1999). International travel and health : vaccination requirements and health advice : situation as on 1 January 1999. auth., Geneva: .
MLA
WHO, . International travel and health : vaccination requirements and health advice : situation as on 1 January 1999. auth., Geneva: . 1999.