M. Scott Peck (2002). “The Road Less Traveled, 25th Anniversary Edition: A New Psychology of Love, Traditional Values, and Spiritual Growth”, p.75, Simon and Schuster
Cesar Millan, Melissa Jo Peltier (2006). “Cesar's Way: The Natural, Everyday Guide to Understanding and Correcting Common Dog Problems”, p.215, Crown Archetype
Daniel J. Siegel, Tina Payne Bryson (2011). “The Whole-Brain Child: 12 Revolutionary Strategies to Nurture Your Child's Developing Mind”, p.139, Delacorte Press