Palmer, James O.
Wiley, 1983
Buku Teks
American Psychological Association, 1997
Majalah, Jurnal, Buletin
American Psychological Association, Inc.,, 2002
Majalah, Jurnal, Buletin
Majalah, Jurnal, Buletin
Nietzel, Michael T.
Prentice-Hall, 1998
Buku Teks