Biehler, Robert F.
Houghton Miffiln, [date of publication not identified]
Buku Teks
Blum, Milton L., author
Harper & Row, 1968
Buku Teks
Riggio, Ronald E., author
Pearson, 2009
Buku Teks
The British Psychological Society, 2018
Majalah, Jurnal, Buletin
editor-in-chief Charles D. Spielberger
Hershey, 2004
Buku Teks