Kornblum, William
Harcourt Brace College Publishers, 1997
Buku Teks SO
Bryjak, George J
Allyn and Bacon, 1994
Buku Teks SO
Calhoun, Craig J.
McGraw-Hill , 1994
Buku Teks
Farley, John E.
Prentice-Hall, 1992
Buku Teks SO
Nobbs, Jack
Macmillan Education, Ltd., 1989
Buku Teks SO