Wilkes, Angela
Passport Books, 1987
Buku Teks SO
Rybak, Stephanie
Macmillan, 1985
Buku Teks SO
Barratt, William B.
Aldine House, 1994
Buku Teks
Whitmarsh, W.F.H.
Longmans, Green, 1960
Buku Teks SO
Spencer, R.A.
Edward Arnold, [Date of publication not identified]
Buku Teks SO