Theodore Roosevelt (2015). “Theodore Roosevelt on Bravery: Lessons from the Most Courageous Leader of the Twentieth Century”, p.13, Skyhorse Publishing, Inc.
Henry David Thoreau, Barry Andrews (2005). “True Harvest: Readings from Henry David Thoreau for Every Day of the Year”, p.71, Unitarian Universalist Association of Congregations
H. Jackson Brown, Jr. (2012). “Life's Little Instruction Book: Simple Wisdom and a Little Humor for Living a Happy and Rewarding Life”, p.75, Thomas Nelson Inc
Orison Swett Marden (2015). “ORISON SWETT MARDEN Premium Collection - Wisdom & Empowerment Series (18 Books in One Volume): Steps to Success and Power, How to Get What You Want, An Iron Will, Be Good to Yourself, Every Man A King, Keeping Fit, Prosperity – How to Attract It, Stepping-Stones To Fame And Fortune...”, p.873, e-artnow