Mass., A. J. St. Onge, 1970
Buku Teks
Friedrich, Carl J.
Boston University Press, 1967
Buku Teks
Graber, Mark A.
Oxford University Press, 2015
Buku Teks
Dumbauld, Edward
University of Oklahoma Press, 1950
Buku Teks
D.C. Heath and Company, 1976
Buku Teks