Stephen Mansfield
Michigan : Baker Book House, 2017
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Enright, Robert D., author
APA LifeTools, 2005
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Hryniewicz, Waclaw
Council for Research in Values and Philosophy, 2007
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Motinggo, Quito R., author
Mizan, 2005
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Lee, Gyu Tae, author
Shinwon Munwhasa, 2009
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