Wayne W. Dyer (2009). “The Invisible Force: 365 Ways to Apply the Power of Intention to Your Life: Easyread Super Large 24pt Edition”, p.275, ReadHowYouWant.com
Alan Greenspan's speech at the Annual Dinner and Francis Boyer Lecture of The American Enterprise Institute for Public Policy Research in Washington, D.C., www.federalreserve.gov. December 5, 1996.