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Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, pp. 64–9 (cf. Donald Routledge Hill, Mechanical EngineeringArchived 25 December 2007 at the Wayback Machine)
Georges Ifrah (2001). The Universal History of Computing: From the Abacus to the Quantum Computer, p. 171, Trans. E.F. Harding, John Wiley & Sons, Inc. (See [1])