Spencer, R.A., author
Edward Arnold, [Date of publication not identified]
Buku Teks
Rybak, Stephanie, author
Macmillan, 1985
Buku Teks
Barratt, William B., author
Aldine House, 1994
Buku Teks
Whitmarsh, W.F.H., author
Longmans, Green, 1960
Buku Teks
Skaife, Linda, author
National Textbook Company, 1994
Buku Teks