Tippett-Spirtou, Sandy, author
Routledge, 1999
Buku Teks
Coultas, Barbara, author
Teach Yourself Books, 1990
Buku Teks
Moffatt, C.W. Paget
University Tutorial Press, 1`929
Buku Teks
Barratt, William B.
Aldine House, 1994
Buku Teks
Graham, Gaelle, author
Hodder & Stoughton, 1991
Buku Teks