Address at the Sorbonne, Paris, 23 Apr. 1910. Richard M. Nixon quoted this passage in his address to the nation announcing his decision to resign the presidency, 8 Aug. 1974. See Theodore Roosevelt 1; Theodore Roosevelt 2; Theodore Roosevelt 5
Jack Canfield, Mark Victor Hansen, Amy Newmark (2011). “Chicken Soup for the Soul: Preteens Talk: Inspiration and Support for Preteens from Kids Just Like Them”, p.349, Simon and Schuster