James C. Humes, Benjamin Franklin (1995). “The wit and wisdom of Benjamin Franklin: a treasury of more than 900 quotations and anecdotes”, Harpercollins
Albert Einstein (2015). “Bite-Size Einstein: Quotations on Just About Everything from the Greatest Mind of the Twentieth Century”, p.14, St. Martin's Press
Albert Einstein (2015). “Bite-Size Einstein: Quotations on Just About Everything from the Greatest Mind of the Twentieth Century”, p.31, St. Martin's Press