Ralby, Aaron, author
Parragon Books, 2013
Buku Referensi
Alic, Margaret
The Women's Press , 1986
Buku Teks
Feder, Kenneth L.
Mayfield Publishing Company, 1997
Buku Teks
Spring, Joel, author
McGraw-Hill, 2008
Buku Teks
Americana Corporation, 1980
Buku Referensi