Hays, S. (1972). #aConservation and the gospel of efficiency: The progressive conservation movement, 1890-1920. Atheneum.
Citace podle Chicago (17th ed.)Hays, Samuel. #aConservation and the Gospel of Efficiency: The Progressive Conservation Movement, 1890-1920. New York: Atheneum, 1972.
Citace podle MLA (9th ed.)Hays, Samuel. #aConservation and the Gospel of Efficiency: The Progressive Conservation Movement, 1890-1920. Atheneum, 1972.
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