Hurd, P. D. (1961). Biological education in American secondary schools, 1890-1960. American Institute of Biological Sciences.
Citace podle Chicago (17th ed.)Hurd, Paul DeHart. Biological Education in American Secondary Schools, 1890-1960. Washington: American Institute of Biological Sciences, 1961.
Citace podle MLA (8th ed.)Hurd, Paul DeHart. Biological Education in American Secondary Schools, 1890-1960. American Institute of Biological Sciences, 1961.
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