Wayne W. Dyer (2009). “Being in Balance: 9 Principles for Creating Habits to Match Your Desires: Easyread Super Large 24pt Edition”, p.131, ReadHowYouWant.com
Sylvia Boorstein, Ph.D. (2007). “Pay Attention, for Goodness' Sake: Practicing the Perfections of the Heart--The Buddhist Path of Kindness”, p.69, Ballantine Books