Denning, Melita
Llewellyn Publications, 1993
Buku Teks
Kaplan, Burton, author
Prentice-Hall, 1995
Buku Teks
Mortensen, Kurt W., author
American Management Association, 2013
eBooks
Reed, Scott
N.Y Parker Pub. Co., 1972
Buku Teks
Scott, Steven K.
Think, 2006
Buku Teks