Sydanmaanlakka, Pentti
Capstone Publishing Limited (a Wiley company), 2002
Buku Teks
Gallagher, John P.
Prentice-Hall, 1988
Buku Teks
Scholz, Roland W.
Sage, 2002
Buku Teks
Howes, Norman R.
[American Management Association, ], 2001
eBooks
Cronin, Patricia
Mosby , 2004
Buku Teks