Theodore Roosevelt (2015). “Theodore Roosevelt on Bravery: Lessons from the Most Courageous Leader of the Twentieth Century”, p.42, Skyhorse Publishing, Inc.
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