APA

Fisher R. M., National Geographic Society U.S, . (1991). Heartland of a continent: America's Plains and pairies. Washington, D.C: National Geographic Society.

Chicago

Fisher Ronald M, National Geographic Society U.S, . 1991. Heartland of a continent: America's Plains and pairies. Washington, D.C: National Geographic Society.

Harvard

Fisher R. M., National Geographic Society U.S, . (1991). Heartland of a continent: America's Plains and pairies. Washington, D.C: National Geographic Society.

MLA

Fisher Ronald M, National Geographic Society U.S, . Heartland of a continent: America's Plains and pairies. Washington, D.C: National Geographic Society. 1991.