United States. National Park Service. & Yard, R. S. (1917). The national parks portfolio ([2nd ed.].). U.S. Govt. Print. Off..
MLA CitationUnited States. National Park Service. and Robert Sterling Yard. The National Parks Portfolio. [2nd ed.]. U.S. Govt. Print. Off., 1917.
Warning: These citations have been automatically generated and may not always be 100% accurate..