Schoch, Elizabeth T.
Adam Media Corporation, 2002
Buku Teks
Warren, Bruce, author
Wadsworth and Cengage Learning, 2013
Buku Teks
edited by Agosto
Rockport, 1998
Buku Teks
Kelby, Scott, author
Prigel books, 2013
Buku Teks
Odam, John, author
Peachpit, 1999
Buku Referensi