Henry David Thoreau, Barry Andrews (2005). “True Harvest: Readings from Henry David Thoreau for Every Day of the Year”, p.125, Unitarian Universalist Association of Congregations
Mark Twain (2014). “Mark Twain on Common Sense: Timeless Advice and Words of Wisdom from America's Most-Revered Humorist”, p.27, Skyhorse Publishing, Inc.