Marie Curie's letter to Eve Curie Labouisse (July 1929), as quoted in Eve Curie Labouisse "Madame Curie: A Biography" translated by Vincent Sheean (p. 341), 1937.
George Bernard Shaw (2015). “George Bernard Shaw: The Collected Plays (Illustrated): 60 plays including Caesar and Cleopatra, Pygmalion, Saint Joan, The Apple Cart, Cymbeline, Androcles And The Lion, The Man Of Destiny, The Inca Of Perusalem and Macbeth Skit”, p.2005, e-artnow
"Warren Buffett: I Haven't Seen As Much Economic Fear In My Adult Lifetime - Charlie Rose Interview". Interview with Charlie Rose, www.cnbc.com. October 1, 2008.