Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, 1991/05, pp. 64-9 (Donald Routledge Hill, Mechanical EngineeringArchyvuota kopija 2007-12-25 iš Wayback Machine projekto.)
web.archive.org
Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, 1991/05, pp. 64-9 (Donald Routledge Hill, Mechanical EngineeringArchyvuota kopija 2007-12-25 iš Wayback Machine projekto.)