Andy Mantell, Terry Scragg, editor
Learning matters Ltd., 2008
Buku Teks
Wickham, Randall Easton, author
Sage publications , 2002
Buku Teks
Seden, Janet, author
Open University Press, 2005
Buku Teks
Smith, David
Macmillan, 1995
Buku Teks
edited by Bob Franklin
Routledge, 1991
Buku Teks