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
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
Cassandra Clare (2012). “Cassandra Clare: The Mortal Instruments Series (5 books): City of Bones; City of Ashes; City of Glass; City of Fallen Angels, City of Lost Souls”, p.1372, Simon and Schuster
Socrates, Plato, Aristotle (1967). “Wit and Wisdom of Socrates, Plato, Aristotle: Being a Treasury of Thousands of Glorious, Inspiring and Imperishable Thoughts, Views and Observations of the Three Great Greek Philosophers, Classified Under about Four Hundred Subjects for Comparative Study”