Benjamin, Jane
Fourmat Publishing, 1993
Buku Teks
Pritchard, John
Viking, 1992
Buku Referensi
general editor Michael Renshall
Butterworth, 1990
Buku Referensi
Barnes, A. James
Homewood, Ill., Learning Systems
Buku Teks
Twomey, David P.
South-Western Publishing Company, 1986
Buku Teks