Griffiths, Peter, author
Facet, 2004
Buku Teks
Smith, John W. T., author
International Thomson, 1994
Buku Teks
Holden, Greg, author
American Management Association, 2008
eBooks
Angell, David, author
IDG Books, 1995
Buku Teks
Sanders, Jack, 1944-, author
Ragged Mountain Press/McGraw-Hill, 2000
Buku Referensi