Pojman, Louis P., author
McGraw-Hill , 2003
Buku Teks
Schippers, Birgit, author
Routledge, 2014
Buku Teks
edited by Carl J. Friedrich
The Modern Library, 1949
Buku Teks
Kymlicka, Will, author
Clarendon Press, 1990
Buku Teks
Tannenbaum, Donald G., author
Wadsworth/Thomson learning, 2004
Buku Teks