Blank, Steve, author
K & S Rench, Inc Publishers, 2012
Buku Teks
Porter, Lindsay, author
Porter Publishing, 1995
Buku Referensi
Ang, Tom, author
Mitchell Beazley, 1999
Buku Referensi
Drago, Carl, author
Blackwell Publishing, 2007
Buku Referensi
Ziegler, Kathleen, author
Rockport Publishers, 1994
Buku Referensi