Benjamin, Jane
Fourmat Publishing, 1993
Buku Teks
edited by Richard Haigh, Dai Harris
Routledge, 1994
Buku Teks
Barnes, A. James
Homewood, Ill., Learning Systems
Buku Teks
Twomey, David P.
South-Western Publishing Company, 1986
Buku Teks
Carvan, John
LBC Information Service, 1997
Buku Teks