National geographic's guide to the national parks of the United States.
APA Citation
National Geographic Society (U.S.). (1992). National geographic's guide to the national parks of the United States. Rev. ed. Washington, D.C.: National Geographic Society.
MLA Citation
National Geographic Society (U.S.). National Geographic's Guide to the National Parks of the United States. Rev. ed. Washington, D.C.: National Geographic Society, 1992.
Warning: These citations may not always be complete (especially for serials).