Hutchinson, John G.
Holt, Rinehart and Winston, 1967
Buku Teks
Rue, Leslie W., author
McGraw-Hill Publishing Company, Ltd., 1989
Buku Teks
David, Fred R., author
Pearson, 2009
Buku Teks
David, Fred R., author
Prentice-Hall, 2003
Buku Teks
Wortman, Max Sidones, 1932-
Macmillan, 1969
Buku Teks