Albert Einstein (2015). “Bite-Size Einstein: Quotations on Just About Everything from the Greatest Mind of the Twentieth Century”, p.32, St. Martin's Press
Albert Einstein's speech made in honor of Thomas Mann, when Mann was given the Einstein Prize given by the Jewish Forum (January 1939), as quoted in Abraham Pais "Einstein Lived Here" (p. 214), 1994.
Albert Einstein (2015). “Bite-Size Einstein: Quotations on Just About Everything from the Greatest Mind of the Twentieth Century”, p.15, St. Martin's Press