Sylvia, Ronald D.
Harcourt College Publisher, 2002
Buku Teks
Cayer, N. Joseph
Wadsworth/Thomson Learning, 2004
Buku Teks SO
Pfiffner, John M.
Ronald Press, 1960
Buku Teks
edited by Robert T. Golembiewski, Frank Gibson, Geoffrey Y. Cornog
Rand McNally College, 1972
Buku Teks
Simon, Herbert A.
Alfred A. Knopf, 1973
Buku Teks