Barton, Jonathan R.
Routledge, 1997
Buku Teks
edited by Louis W. Goodman, William M. LeoGrande, Johanna Mendelson Forman
Westview Press, 1992
Buku Teks
Busey, James L., author
Random House, 1968
Buku Teks
Schwartz, Bernard, author
McGraw-Hill, 1974
Buku Teks
Posner, Richard A., author
Clarendon Press, 1996
Buku Teks