"Archived copy". www.geocities.com. Archived from the original on 1 December 2007. Retrieved 11 January 2022.{{cite web}}: CS1 maint: archived copy as title (link)
Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, pp. 64–69. (cf. Donald Routledge Hill, Mechanical EngineeringArchived 2007-12-25 at the Wayback Machine)
"Archived copy". www.geocities.com. Archived from the original on 1 December 2007. Retrieved 11 January 2022.{{cite web}}: CS1 maint: archived copy as title (link)
Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, pp. 64–69. (cf. Donald Routledge Hill, Mechanical EngineeringArchived 2007-12-25 at the Wayback Machine)