Quah, Jon S. T., author
Talisman Pub, 2010
Buku Teks
Quah, Jon S. T., author
Emerald, 2010
Buku Teks
Pfiffner, John M., author
Ronald Press, 1960
Buku Teks
edited by Robert T. Golembiewski, Frank Gibson, Geoffrey Y. Cornog
Rand McNally College, 1972
Buku Teks
Simon, Herbert A., author
Alfred A. Knopf, 1973
Buku Teks