Randolph Spencer Churchill, Winston Churchill, Martin Gilbert (1983). “Winston S. Churchill: Companion Vol. V, Part Three, the Coming of War 1936-1939”, Houghton Mifflin Harcourt (HMH)
Albert Einstein (2015). “Bite-Size Einstein: Quotations on Just About Everything from the Greatest Mind of the Twentieth Century”, p.33, St. Martin's Press
"The Ballot or The Bullet (Cleveland Version)". Malcolm X's speech at Cory Methodist Church in Cleveland, Ohio (April 3, 1964) as quoted in "Malcolm X Speaks: Selected Speeches and Statements" edited by George Breitman (pp. 23-44), 1965.