Kottke, Frederic J.
W.B. Saunders Company, 1990
Buku Referensi
Barash, Paul G.
New York : Lippincott, 1997,
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Spickett, Gavin
Oxford University Press, 1999
Buku Referensi
edited by Samuel M. Turner, Karen S. Calhoun, Henry E. Adams
John Wiley & Sons, 1992
Buku Referensi
Barash, Paul G.
Lippincott - Raven Publishers, 1997
Buku Referensi