Mark Twain (2014). “Mark Twain on Common Sense: Timeless Advice and Words of Wisdom from America's Most-Revered Humorist”, p.37, Skyhorse Publishing, Inc.
Erwin Raphael McManus (2004). “The Uprising Experience: A Personal Guide for a Revolution of the Soul, Promise Keepers Edition”, p.52, Thomas Nelson 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