Sage Publications , 2001
Majalah, Jurnal, Buletin
Fiona Macmillan
Sweet & Maxwell, 2005
Buku Teks
Macmillan, Fiona, author
Aweet & Maxwell, 2001
Buku Teks
Miller, G. Tyler (George Tyler), 1931-, author
Brooks/Cole Cengage Learning, 2012
Buku Teks
Beatty, Jeffrey F., author
South Western Cengage Learning, 2011
Buku Teks