1. Philosophical Quarterly, 1959, p. 302.
2. Eves H. : An Introduction to the History of Mathematics, p. 261.
3. The Foundations of Arithmetic (tr. b y Austin J. L. ), § 31.
4. Kneale W. (Probability and Induction, p. 37) thinks the principle was formulated by Fermat, and no doubt has this passage in mind.
5. First edition; Second edition, p. 165-6.