W. E. B. Du Bois (2014). “The Problem of the Color Line at the Turn of the Twentieth Century: The Essential Early Essays”, p.59, Oxford University Press
John D. Rockefeller (2015). “John D. Rockefeller on Making Money: Advice and Words of Wisdom on Building and Sharing Wealth”, p.30, 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