Gewirtz, Herman
Barron`s, 1994
Buku Teks SO
Arons, Arnold B.
John Wiley & Sons, 1990
Buku Teks SO
California Research and Education Association, 1995
Buku Teks SO
edited by Thomas L. O'Kuma, David P. Maloney and Curtis J. Hieggelke
Prentice-Hall, 2000
Buku Teks SO
Heddle, Trevor
Pergamon Press, 1971
Buku Teks SO