Metzler, Lloyd A.
W.W. Norton & Company Inc. , 1948
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
Denhardt, Robert B.
Harcourt College, 1999
Buku Teks