James, David Gwilyn, author
Geoffrey Cumberlege, 1948
Buku Teks
Greenlaw, Paul S.
New York, N.Y. Harper & Row 1986,
Buku Teks
Brown, John Seely
Harvard Business School Press, 2000
Buku Teks
Bahn, Paul, author
Thames and Hudson , 1992
Buku Teks
Osborne, Adam, author
Osborne McGraw-Hill, 1981
Buku Teks