Parkwide road improvement plan :
Yellowstone National Park, Wyoming/Montana/Idaho.

APA Citation

United States. National Park Service. (1992). Parkwide road improvement plan: Yellowstone National Park, Wyoming/Montana/Idaho. [Washington, D.C.?]: U.S. Dept. of the Interior, National Park Service.

MLA Citation

United States. National Park Service. Parkwide Road Improvement Plan: Yellowstone National Park, Wyoming/Montana/Idaho. [Washington, D.C.?]: U.S. Dept. of the Interior, National Park Service, 1992.

Warning: These citations may not always be complete (especially for serials).