Sabino, Catherine
Thomes and Hudson, 1986
Buku Referensi
Bocchetta, Vittore E.
Follett Publishing Company, 1987
Buku Referensi
Certoma, G. Leroy
Butterworth, 1985
Buku Teks
Borrie, W.D.
F.W. Chesire, 1954
Buku Teks
London English University Press 1958
Buku Teks