Jennings, Marianne Moody, author
South-Western, 2009
Buku Teks
Wallace, Catherine, author
1992
Buku Teks
Wallace, Catherine, author
Oxford University Press, 1993
Buku Teks
Business Publications, Inc., 1984
Buku Teks
Crowther, Geoffrey
Thomas Nelson and Sons Ltd , 1949
Buku Teks