"Banach Spaces and Their Applications in Analysis: Proceedings of the International Conference at Miami University, May 22-27, 2006, in Honor of Nigel Kalton's 60th Birthday" by Beata Randrianantoanina, Narcisse Randrianantoanina, Walter de Gruyter, (p. 5), 2007.

"Mathematical Games". Scientific American (October 1973), later quoted in Roger B. Nelson "Proofs Without Words: Exercises in Visual Thinking" ("Introduction", p. 5), 1993.