Albert Einstein, Anna Beck, Peter Havas (1987). “The Collected Papers of Albert Einstein: The early years, 1879-1902”, p.15, Princeton University Press
Albert Einstein, Stephen W. Hawking (2007). “A Stubbornly Persistent Illusion: The Essential Scientific Works of Albert Einstein”, p.337, Running Press
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
Back to Methuselah pt. 1, act 1 (1921). This was a favorite quotation of Robert F. Kennedy's, and Edward M. Kennedy used it in his eulogy of Robert Kennedy.