Henry David Thoreau (2014). “Citizen Thoreau: Walden, Civil Disobedience, Life Without Principle, Slavery in Massachusetts, A Plea for Captain John Brown”, p.72, Graphic Arts Books
Joshua Lawrence Chamberlain, Jeremiah E. Goulka (2004). “The grand old man of Maine: selected letters of Joshua Lawrence Chamberlain, 1865-1914”, The University of North Carolina Press