lyons, stanley, author
Butterworth-Heinemann Ltd., 1992
Buku Referensi
Pritchard, David C., author
Longman, 1995
Buku Teks
Pritchard, David C., author
Longman, 1995
Buku Teks
Niesewand, Nonie, author
Mitchell Beazley, 1999
Buku Referensi
Watson, Lee, author
McGraw-Hill, 1990
Buku Referensi