Buku Teks
Hanks, Lucien M
Aldine Atherton, 1972
Buku Teks SO
Wojciechowski, Jerzy A.
Council for research in values and philosophy, [Date of publication not identified]
Buku Teks SO
Odum, Eugene Pleasants
Saunders College, 1983
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Pianka, Eric R.
Harper & Row, 1988
Buku Teks