edited by Carl J. Friedrich, Robert G. McCloskey
The Liberal Arts Press, 1954
Buku Teks
Berliner, Baruch, author
Prentice-Hall, 1982
Buku Teks
Krishnamurti, J. (Jiddu), 1895-1986, author
New York Routledge , 1999
Buku Teks
by Mandy Swann [and others]
McGraw-Hill, 2012
Buku Teks
Sandel, Michael J., author
Cambridge University Press, 2010
Buku Teks