APA
WHO, . (1997). International travel and health : Vaccination requirements and health advice. auth., Geneva: .
Chicago
WHO, . 1997. International travel and health : Vaccination requirements and health advice. auth., Geneva: .
Harvard
WHO, . (1997). International travel and health : Vaccination requirements and health advice. auth., Geneva: .
MLA
WHO, . International travel and health : Vaccination requirements and health advice. auth., Geneva: . 1997.