Aktivitas Howard pada Perang Dunia II meliputi akting dan membuat film. Ia aktif dalam propaganda anti-Jerman dan dirumarkan memiliki keterkaitan dengan Intelijensi Sekutu atau Inggris, yang mendatangkan teori konspirasi terkait kematiannya pada 1943 di tangan LuftwaffeJerman saat pesawat Inggris yang ia tumpangi ditembak di Teluk Biscay.
Churchill, Winston S. The Hinge of Fate. New York: Houghton-Mifflin, 1950.
Colvin Ian. Admiral Canaris: Chief of Intelligence. London: Colvin Press, 2007. ISBN 978-1-4067-5821-4.
Colvin Ian. Flight 777: The Mystery Of Leslie Howard. London: Evans Brothers, 1957.
Covington, Howard E., Jr. Lady on the Hill: How Biltmore Estate Became an American Icon. Hoboken, New Jersey: Wiley, 2006. ISBN 978-0-471-75818-1.
Eforgan, Estel. Leslie Howard: The Lost Actor. London: Vallentine Mitchell Publishers, 2010. ISBN 978-0-85303-941-9.
Goss, Chris. Bloody Biscay: The Story of the Luftwaffe's Only Long Range Maritime Fighter Unit, V Gruppe/Kampfgeschwader 40, and Its Adversaries 1942–1944. London: Crécy Publishing, 2001. ISBN 0-947554-87-4.
Howard, Leslie, ed. with Ronald Howard. Trivial Fond Records. London: William Kimber & Co Ltd, 1982. ISBN 978-0-7183-0418-8.
Howard, Leslie Ruth. A Quite Remarkable Father: A Biography of Leslie Howard. New York: Harcourt Brace and Co., 1959.
Howard, Ronald. In Search of My Father: A Portrait of Leslie Howard. London: St. Martin's Press, 1984. ISBN 0-312-41161-8.
Macdonald, Bill. The True Intrepid: Sir William Stephenson and the Unknown Agents. Vancouver, BC: Raincoast Books 2002, ISBN 1-55192-418-8.
Noble, Peter, ed. British Film Yearbook for 1945. London: The British Broadcasting Corporation, 1945.
Rey Ximena, José. El Vuolo de Ibis [The Flight of the Ibis] (Spanyol). Madrid: Facta Ediciones SL, 2008. ISBN 978-84-934875-1-5.
Rosevink, Ben and Lt Col Herbert Hintze. "Flight 777" .FlyPast, Issue #120, July 1991.
Sklar, Robert. City Boys: Cagney, Bogart, Garfield. Princeton, New Jersey: Princeton University Press, 1992. ISBN 0-691-04795-2].
Smith, Joseph B. Portrait of a Cold Warrior. New York: Random House, 1976. ISBN 978-0-399-11788-6.
Southall, Ivan. They Shall Not Pass Unseen. London: Angus and Robertson, 1956.
Stevenson, William. A Man Called Intrepid: The Incredible World War II Narrative of the Hero Whose Spy Network and Secret Diplomacy Changed the Course of History. Guilford, Delaware: Lyons Press, 1976, reissued in 2000. ISBN 1-58574-154-X.
Verrier, Anthony. Assassination in Algiers: Churchill, Roosevelt, De Gaulle, and the Murder of Admiral Darlan. New York: W. W. Norton and Company, Inc., 1st edition, 1991. ISBN 978-0-393-02828-7.
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