Biehler, Robert F.
Houghton Miffiln, [date of publication not identified]
Buku Teks SO
Snowman, Jack, author
Wadsworth and Cengage Learning, 2012
Buku Teks
Kolb, David A., author
Prentice-Hall, 1974
Buku Teks
Nicolson, Paula, author
MacMillan Education, 1986
Buku Teks SO
Gilmer, B. von Haller (Beverly von Haller), 1909-1994, author
McGraw-Hill, 1967
Buku Teks SO