Olga Aikin
IPM, 1994
Buku Teks
Clarke, Linda, author
Institute of Personnel and Development, 1993
Buku Teks
Hand, D.J., author
John Wiley & Sons, 1981
Buku Teks
Fredman, Sandra, author
Oxford University Press, 2011
Buku Teks
edited by Craig Donnellan
Independence Educational, 1995
Buku Teks