Allen, S. W., & Leonard, J. W. (1966). Conserving natural resources (3rd ed.). New York: McGraw-Hill.
Παραπομπή Chicago StyleAllen, Shirley Walter, and Justin Wilkinson Leonard. Conserving Natural Resources. 3rd ed. New York: McGraw-Hill, 1966.
Παραπομπή MLAAllen, Shirley Walter, and Justin Wilkinson Leonard. Conserving Natural Resources. 3rd ed. New York: McGraw-Hill, 1966.
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