Will Rogers, Bryan B. Sterling, Frances N. Sterling (1993). “Will Rogers' World: America's Foremost Political Humorist Comments on the Twenties and Thirties--and Eighties and Nineties”, p.25, Rowman & Littlefield
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)