George Carlin (2015). “3 x Carlin: An Orgy of George including Brain Droppings, Napalm and Silly Putty, and When Will Jesus Bring the Pork Chops?”, p.197, Hachette UK
George Orwell (2001). “The Complete Novels of George Orwell: Animal Farm, Burmese Days, A Clergyman's Daughter, Coming Up for Air, Keep the Aspidistra Flying, Nineteen Eighty-Four”, p.21, Penguin UK
Roderick Impey Murchison (1854). “Siluria the History of the Oldest Known Rocks Containing Organic Remains, with a Brief Sketch of the Distribution of Gold Over the Earth by Roderick Impey Murchison”, p.5
George Gaylord Simpson (1967). “The Meaning of Evolution: A Study of the History of Life and of Its Significance for Man”, p.311, Yale University Press