Harvard Business School , 2000
Buku Teks
Steele, Paul
McGraw-Hill Book , 1996
Buku Teks
Olsen, Michael D., author
Prentice-Hall, 2008
Buku Teks
Gaynor, Gerard H., author
American Management Association, 2004
eBooks
Hosmer, LaRue T.
Prentice-Hall, 1982
Buku Teks