Butler, G. D. (1936). Playgrounds, their administration and operation: National recreation association. A.S. Barnes.
Citace podle Chicago (17th ed.)Butler, George D. Playgrounds, Their Administration and Operation: National Recreation Association. New York: A.S. Barnes, 1936.
Citace podle MLA (8th ed.)Butler, George D. Playgrounds, Their Administration and Operation: National Recreation Association. A.S. Barnes, 1936.
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