H. Jackson Brown, Jr. (2012). “Life's Little Instruction Book: Simple Wisdom and a Little Humor for Living a Happy and Rewarding Life”, p.75, Thomas Nelson Inc
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.
Dr. Robert C. Worstell, Dorothea Brande, Claude M. Bristol, Earl Nightingale, Napoleon Hill (2017). “Mindset StackingTM Inspirational Journal VolumeSS01”, p.60, Lulu.com