Cambridge University Press, 2007
eBooks
Maxwell, Rhoda J.
Allyn and Bacon, 1999
Buku Teks
Gunner, Jeanne
Harper & Row, 1986
Buku Teks
Kelly, Curtis, author
Cambridge university press, 2008
Buku Teks
Kelly, Curtis, author
Cambridge university press, 2010
Buku Teks