Coultas, Barbara
Teach Yourself Books, 1990
Buku Teks
Rybak, Stephanie
Macmillan, 1985
Buku Teks
Barratt, William B.
Aldine House, 1994
Buku Teks
Whitmarsh, W.F.H.
Longmans, Green, 1960
Buku Teks
Spencer, R.A.
Edward Arnold, [Date of publication not identified]
Buku Teks