Carpenter, Catrine, author
McGraw-Hill, 2004
Buku Teks
Wilkes, Angela
Passport Books, 1987
Buku Teks
Wilkes, Angela
[date of publication not identified]
Buku Teks
Coultas, Barbara, author
Teach Yourself Books, 1990
Buku Teks
Bladon, Rachel, author
Passport Books, [Date of publication not identified]
Buku Teks