Stim, Richard, author
West Thomson Learning, 2001
Buku Referensi
Schechter, Roger E., author
Thomson West, 2003
Buku Teks
Kintner, Earl W., author
Macmillan, 1975
Buku Teks
Bainbridge, David, author
Pearson - Longman, 2002
Buku Teks
Eastaway, Nigel, author
Sweet & Maxwell, 2008
Buku Teks