Bruce, R. Robert
Hodder & Stoughton, 1994
Buku Teks
Coggle, Paul
Teach Youeself Books, 1991
Buku Teks SO
Bhatia, Tej K.
Routledge, 2000
Buku Teks SO
Graham, Gaelle
Hodder & Stoughton, 1991
Buku Teks SO
Evans, Joyce J.
John Wiley & Sons, 2003
Buku Teks