Morkuniene, Jurate
Council for Research in Values and Philosophy, 2004
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Donovan, Todd, author
Wadsworth and Cengage Learning, 2014
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Shiraev, Eric B., author
Pearson/Allyn and Bacon, 2004
Buku Teks SO
edited by Lawrence S. Wringtsman
Wadsworth, 1968
Buku Teks
Parrillo, Vincent N., author
John Wiley & Sons, 1985
Buku Teks