Dale, Margaret, author
Kogan Page Limited, 2003
Buku Teks
Weston, J. Fred (John Fred), 1916-, author
ESG , 1981
Buku Teks
Williams, Carolyn L., author
American Psychological Association , 2011
Buku Teks
Wallis, W.D., author
Springer, 2012
eBooks
Stapleton, Gerald F., author
Tab Books, 1971
Buku Referensi