Cullen, Pauline, author
Cambridge University Press, 2008
Multimedia
Clark, John Willis, author
Cambridge University Press, 2009
eBooks
Cullen, Pauline, author
Cambridge university press, 2010
Buku Teks
Hopkins, Diana, author
Cambridge University Press, 2011
Buku Teks
editor, Peter Pagnamenta
Third Millennium Publishing, 2008
Buku Referensi