APA
, . (1977). National Geographic index, 1947-1976. Washington, D.C. (17th & M Sts., N.W., Washington 20036): National Geographic Society.
Chicago
, . 1977. National Geographic index, 1947-1976. Washington, D.C. (17th & M Sts., N.W., Washington 20036): National Geographic Society.
Harvard
, . (1977). National Geographic index, 1947-1976. Washington, D.C. (17th & M Sts., N.W., Washington 20036): National Geographic Society.
MLA
, . National Geographic index, 1947-1976. Washington, D.C. (17th & M Sts., N.W., Washington 20036): National Geographic Society. 1977.