Links
An interesting Museum of Calculating Devices to visit:
http://www.calculators.de/
A history of the abacus:
http://www.ee.ryerson.ca:8080/~elf/abacus/
Further reading
Smith, D.E., History of Mathematics, Vol II (Dover 1958).
Cameron, M., Heritage Mathematics (Hargreen, 1983).
Menninger, K., Number Words and Number Symbols (MIT Press, 1969).
