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.43, Hachette UK
Quoted in Bennett Cerf, Try and Stop Me: A Collection of Anecdotes and Stories, Mostly Humorous (1944). Although this is usually credited to Mizner, the Los Angeles Times, 17 Mar. 1941, quotes Bob Oliver: "If you steal from one man, it's plagiarism. If you steal from several, it's research."