1. Isaac Newton, Mathematical Principles of Natural Philosophy, 3rd ed., 1726, tr. A. Motte, revised by Florian Cajori, University of California Press, Berkeley, 1934, Scholium to Lemma XI. p. 39.
2. J. V. Grabiner, The Origins of Cauchy's Rigorous Calculus, M. I. T. Press, Cambridge and London, 1981, chapter 2.