Leaders Magazine,
Majalah, Jurnal, Buletin
Ulrich, David, 1953-, author
John wiley & Sons, Inc, 2003
Buku Teks
editors and contributors, Joseph J. Norton, Thomas L. Bloodworth ; editorial coordinator, Terry K. Pennington
Martinus Nijhoff Publishers, 1995
Buku Teks
Boston : Federal Reserve Bank of Boston, 1998,
Buku Teks
Brown, Gary D., author
John Wiley & Sons, 1981
Buku Teks