APA (7th ed.) Citation

United States. National Park Service, Story, I. F., & Yard, R. S. (1931). The national parks portfolio (6th ed.). U.S. G.P.O..

Chicago Style (17th ed.) Citation

United States. National Park Service, Isabelle F. Story, and Robert Sterling Yard. The National Parks Portfolio. 6th ed. Washington: U.S. G.P.O., 1931.

MLA (9th ed.) Citation

United States. National Park Service, et al. The National Parks Portfolio. 6th ed. U.S. G.P.O., 1931.