McMahon, Linnet
Routledge, 1992
Buku Referensi
Cattanach, Ann
Jessica Kingsley, 1992
Buku Teks SO
Carmichael, Karla D.
Pearson - Prentice Hall, 2006
Buku Teks SO
edited by David A. Crenshaw and Anne L. Stewart ; foreword by Stuart Brown.
The Guilford Press, 2015
Buku Teks
Wilson, Kate
Bailliere Tindall, 1997
Buku Teks SO