Cita APA (7a ed.)

United States. National Park Service & Yard, R. S. (1925). The National parks portfolio (4th ed.). Govt. Pr. Off..

Cita Chicago Style (17a ed.)

United States. National Park Service y Robert Sterling Yard. The National Parks Portfolio. 4th ed. Washington: Govt. Pr. Off., 1925.

Cita MLA (8a ed.)

United States. National Park Service y Robert Sterling Yard. The National Parks Portfolio. 4th ed. Govt. Pr. Off., 1925.

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