O`Neil, John R., author
McGraw-Hill, 1995
Buku Teks
Harvey, Steve, author
Amistad, an imprint of HarperCollinsPublishers, 2014
Buku Teks
Mortensen, Kurt W., author
American Management Association, 2004
eBooks
edited by Curtiss P. Hansen and Kelley A. Conrad
Quorum Books , 1991
Buku Referensi
Branson, Richard, author
Virgin Books, 2007
Buku Teks