Harvard Business School Press, 1998
Buku Teks
Hunt, John W.
McGraw-Hill, 1976
Buku Teks SO
Harvard Business School Press , 2001
Buku Teks
Schneider, Susan C.
Prentice-Hall, 1997
Buku Teks
Jackson, Susan E.
South Westh Western College, 2000
Buku Teks SO