Sealey, Raphael
London The University of North Carolina Press 1990,
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Tran, Van Doan
The council for research in values and philosophy, 2001
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Wagener, Wolfgang
Phaidon, 2002
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Cappeletti, Mauro
The Bobbs - Merrill Company,INC, 1979
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Norri, Alan
Weidenfeld and Nicolson, 1992
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