Jonathan Marsh. <a href="http://www.w3.org/TR/2003/WD-xml-id-req-20030806"><cite>xml:id Requirements.</cite></a> 6 August 2003. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2003/WD-xml-id-req-20030806">http://www.w3.org/TR/2003/WD-xml-id-req-20030806</a>