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http://djm.cc/library/Passages_Life_of_a_Philosopher_Babbage_edited.pdf
3. C.G. Bachet, Problèmes plaisants et délectables, qui se font par les nombres, 2nd edn. (Rigaud, Lyon, 1624),
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4. W.A. Beyer, Review of [7]. Am. Math. Mon. 86, 66–67 (1979)
5. B.D. Blackwood, Charles Babbage. In: ed. by D.R. Franceschetti Biographical Encyclopedia of Mathematicians. (Cavendish, New York, 1998), pp. 33–36,
http://www.blackwood.org/Babbage.htm