"Otto Dix, 1891-1969", exhibition catalogue, London: Tate Gallery, 1992, pp. 17 - 18; as cited by Roy Forward, in "Education resource material: beauty, truth and goodness in Dix's War", p. 9,
Abraham Lincoln, Don Edward Fehrenbacher (1977). “Abraham Lincoln, a Documentary Portrait Through His Speeches and Writings”, p.169, Stanford University Press
Ulysses S. Grant, Harriet Beecher Stowe, Stephen Crane, Jefferson Davis, Abraham Lincoln (2012). “The Modern Library Civil War Bookshelf 5-Book Bundle: Personal Memoirs, Uncle Tom's Cabin, The Red Badge of Courage, Jefferson Davis: The Essential Writings, The Life and Writings of Abraham Lincoln”, p.2829, Modern Library