Coba jelasin Karya dari Robert G. Ingersoll dong

The gods and other lectures (New York : D. M. Bennett, 1876)

Some mistakes of Moses (Washington, D.C. : C. P. Farrell, 1879)

Walt Whitman (New York, The Truth Seeker Co, 1890)

Col. Ingersoll's reply to his critics in the N.Y. "Evening Telegram."  (Toronto : J. Spencer Ellis, 1892)

Shakespeare, a lecture (New York, Farrell, 1895)

Abraham Lincoln, a lecture  (New York, Farrell, 1895)

Voltaire, a lecture (New York, Farrell, 1895)

Great speeches of Col. R. G. Ingersoll; complete (Chicago : Rhodes & McClure, 1895)

"Why I am an agnostic" (1896)

The works of Robert G. Ingersoll vols. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 (New York : The Dresden pub. co., C. P. Farrell, 1902)

Nathan G. Alexander,Race in a Godless World: Atheism, Race, and Civilization, 1850-1914. New York/Manchester: New York University Press/Manchester University Press, 2019.

Eric T. Brandt, Timothy Larsen, "The Old Atheism Revisited: Robert G. Ingersoll and the Bible," Journal of The Historical Society, vol. 11, no. 2 (2011), pp. 211–238.

Eugene V. Debs, "Recollections of Ingersoll," Pearson's Magazine, vol. 37, no. 4 (April 1917), pp. 302–307.

Susan Jacoby, The Great Agnostic: Robert Ingersoll and American Freethought. New Haven, CT: Yale University Press, 2013.

Orvin Larson, American Infidel: Robert G. Ingersoll a Biography. Citadel Press, 1962.

Susan Jacoby, Freethinkers: A History of American Secularism. Metropolitan Books, 2004.