Ian Hacking (2006). “The Emergence of Probability: A Philosophical Study of Early Ideas about Probability, Induction and Statistical Inference”, p.34, Cambridge University Press

Richard P. Feynman, Robert B. Leighton, Matthew Sands (2015). “The Feynman Lectures on Physics, Vol. I: The New Millennium Edition: Mainly Mechanics, Radiation, and Heat”, p.118, Basic Books