Robert Green Ingersoll (1898). “Lectures of Col. R.G. Ingersoll: Including His Letters on the Chinese God--Is Suicide a Sin?--The Right to One's Life--etc. Etc. Etc”
P. J. O'Rourke (2007). “Give War a Chance: Eyewitness Accounts of Mankind's Struggle Against Tyranny, Injustice, and Alcohol-Free Beer”, p.21, Grove/Atlantic, Inc.
Bruce D. Perry, Maia Szalavitz (2017). “The Boy Who Was Raised as a Dog: And Other Stories from a Child Psychiatrist's Notebook--What Traumatized Children Can Teach Us About Loss, Love, and Healing”, p.220, Hachette UK