William Lyon Phelps (2016). “A Collection of Classic Essays by William Lyon Phelps - Including 'Happiness', 'Superstition', 'The Great American Game', and Many More”, p.106, Read Books Ltd
Albert Einstein (2015). “Bite-Size Einstein: Quotations on Just About Everything from the Greatest Mind of the Twentieth Century”, p.24, St. Martin's Press
Amby Burfoot (2000). “The Runner's Guide to the Meaning of Life: What 35 Years of Running Have Taught Me About Winning, Losing, Happiness, Humility, and the Human Heart”, p.15, Rodale
George W. Bush's remarks at Arlington Heights, Illinois (October 24, 2000), as quoted in "Bush, in his own words" by Jacob Weisberg, www.theguardian.com. November 3, 2000.