Cohen, Morris Raphael
Free Press, 1950
Buku Teks
Sealey, Raphael, author
London The University of North Carolina Press 1990,
Buku Teks
Tran, Van Doan, author
The council for research in values and philosophy, 2001
Buku Teks
Wagener, Wolfgang, author
Phaidon, 2002
Buku Teks
Cappeletti, Mauro
The Bobbs - Merrill Company,INC, 1979
Buku Teks