Taylor, Ronald L., author
Allyn and Bacon, 2003
Buku Teks
Levinson, Harry, author
Harvard University Press, 1971
Buku Teks
American Psychological Association, 1997
Majalah, Jurnal, Buletin
Gallagher, Richard S., author
American Management Association, 2006
eBooks
edited by Laura A. Cushman and Marcia J. Scherer
American Psychological Association, 1995
Buku Teks