APA
WHO, . (2001). International travel and health : vaccination requirements and health advice : situation as on 1 January 2001. auth., Geneva: .
Chicago
WHO, . 2001. International travel and health : vaccination requirements and health advice : situation as on 1 January 2001. auth., Geneva: .
Harvard
WHO, . (2001). International travel and health : vaccination requirements and health advice : situation as on 1 January 2001. auth., Geneva: .
MLA
WHO, . International travel and health : vaccination requirements and health advice : situation as on 1 January 2001. auth., Geneva: . 2001.