Dunning, James Morse
Harvard University Press, 1980
Buku Teks
Munro, Dana G.
Greewood press, 1964
Buku Teks
Macmillan Press, Ltd., 1994
Buku Teks
Powell, Jim
Writers and readers Publishing, 1997
Buku Teks
Hefferon, Jim
Saint Michaels College, 2000
Buku Teks