Theodore Roosevelt (2015). “Theodore Roosevelt on Bravery: Lessons from the Most Courageous Leader of the Twentieth Century”, p.5, Skyhorse Publishing, Inc.
"Horizon (The Pleasure of Finding Things Out)". Documentary (November 23, 1981), later published in "No Ordinary Genius: The Illustrated Richard Feynman" edited by Christopher Sykes (p. 239), 1994.