Greenberg, Josh, author
Thomson Nelson, 2013
Buku Teks
Daniels, Tom D.
McGraw-Hill, 1997
Buku Teks
edited by Lois Foreman-Wernet, Brenda Dervin
Hampton Press, 2010
Buku Teks
Routledge, 2004
Buku Teks
Anderson, James A., author
McGraw-Hill, 1987
Buku Teks SO