Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, pp. 64-9 (compare Donald Routledge Hill, Mechanical EngineeringArchived 2007-12-25 at the Wayback Machine)
Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, pp. 64-9 (compare Donald Routledge Hill, Mechanical EngineeringArchived 2007-12-25 at the Wayback Machine)