Theodore Roosevelt (2015). “Theodore Roosevelt on Bravery: Lessons from the Most Courageous Leader of the Twentieth Century”, p.42, Skyhorse Publishing, Inc.
Douglas MacArthur's address to the Annual Stockholders Sperry Rand Corporation in New York (July 30, 1957) as quoted in "General MacArthur Speeches and Reports 1908-1964" edited by Edward T. Imparato (p. 206), June 14, 2000.