Cohen, Monique
Sage, 2000
Buku Referensi
Bien, Thomas
Wisdom Publications, 2006
Buku Teks
Nelson-Jones, Richard
Thousand Oaks, California: SAGE, 2014
Buku Teks
Brown, Adrian
Facet Publishing, 2006
Buku Teks
Yerbury, Hilary
University of Technology, 1992
Buku Referensi