1950
Buku Teks
Crawford, Kenneth Grant
University of Toronto Press, 1958
Buku Teks
MacCorkle, Stuart A.
D.C. Heath and Company, 1948
Buku Teks
edited, Alberta M. Sbragia
Westview Press, 1983
Buku Teks
Wilson, Earl R., author
McGraw--Hill , 2010
Buku Teks