Elcock, Howard, author
Longman, 1991
Buku Teks
Mitchell, Ferd H., author
CRC Press, 2016
Buku Teks
editors by Gisela M. von Dran; Jennifer Cargill
The Haworth Press, Inc., 1993
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