Division of Publications, National Park Service, U.S. Dept. of the Interior,
Dorf, Erling, 1905-1984.
United States. National Park Service.
Petrified forests of Yellowstone : Yellowstone National Park, Wyoming, Montana, and Idaho.
Petrified forests of Yellowstone : Yellowstone National Park, Wyoming, Montana, and Idaho.
Petrified forests of Yellowstone :