Longres, John F.
F.E. Peacock Publisher, Inc, 1990
Buku Teks
Germain, Carel Bailey
Columbia Universary Press, 1991
Buku Teks
Sheafor, Bradford W., author
Allyn and Bacon, c2000
Buku Teks
Cohen, Nathan Edward, author
Holt, Rinehart and Winston, 1958
Buku Teks
Johnson, Louise C., 1923-, author
Allyn and Bacon, 1991
Buku Teks