"Umar (634–644)", The Islamic World to 1600 Multimedia History Tutorials by the Applied History Group, University of Calgary. Last accessed 20 Oct 2006Archived 10 April 2007 at the Wayback Machine
"Umar (634–644)", The Islamic World to 1600 Multimedia History Tutorials by the Applied History Group, University of Calgary. Last accessed 20 Oct 2006Archived 10 April 2007 at the Wayback Machine