Wilkes, Angela
Chicago: A Division of NTC Pub., 1987,
Buku Referensi
Coggle, Paul, author
Teach Youeself Books, 1991
Buku Teks
Wilkes, Angela
Passport Books, [date of publication not identified]
Buku Teks
Bladon, Rachel
Passport Books, [date of publication not identified]
Buku Teks
McKeane, Alasdair, author
Longman, 1994
Buku Teks