APA

U. S. Department of the interior. National Park Service, United States, . (1972). Areas nacionales de estudio ambiental. [Washington, D.C.?]: U.S. Dept. of the Interior, National Park Service, Office of Environmental Interpretation.

Chicago

U. S. Department of the interior. National Park Service, United States, . 1972. Areas nacionales de estudio ambiental. [Washington, D.C.?]: U.S. Dept. of the Interior, National Park Service, Office of Environmental Interpretation.

Harvard

U. S. Department of the interior. National Park Service, United States, . (1972). Areas nacionales de estudio ambiental. [Washington, D.C.?]: U.S. Dept. of the Interior, National Park Service, Office of Environmental Interpretation.

MLA

U. S. Department of the interior. National Park Service, United States, . Areas nacionales de estudio ambiental. [Washington, D.C.?]: U.S. Dept. of the Interior, National Park Service, Office of Environmental Interpretation. 1972.