Friederich, Carl J
Cornell University Press, 1957
Buku Teks
Wiarda, Howard J., author
Hartcourt College Publishers, 2001
Buku Teks
Beer, Samuel H., author
Alfred A. Knopf, 1966
Buku Teks
Lipschutz, Ronnie D., author
Routledge, 2005
Buku Teks
edited by Larry W. Bowman and Ian Clark
Westview Press, 1981
Buku Teks