Rene Descartes (2013). “Discourse on the Method: Discourse On the Method of Rightly Conducting the Reason, and Seeking Truth In the Sciences (Beloved Books Edition)”, p.6, Lulu Press, Inc
Ian Hacking (2006). “The Emergence of Probability: A Philosophical Study of Early Ideas about Probability, Induction and Statistical Inference”, p.126, Cambridge University Press