Some Historical Notes on Numbers

1. Origins of some of our concepts of numbers. John H. Conway and Richard K. Guy, The Book of Numbers, Springer, 1996, pp. 1-26.
2. Origins of our present-day numerals. David M. Burton, The History of Mathematics, McGraw-Hill, New York, 1997, pp. 253-255.
3. Cantor. William Dunham, Journey Through Genius, Penguin, New York, 1991, p. 254.
4. Peano's axioms. Carl B. Boyer and Uta C. Merzbach, A History of Mathematics, Wiley, New York, 1991, pp. 596-598.