Daniel Veillard; Jonathan Marsh; Norman Walsh. <a href="http://www.w3.org/TR/2005/REC-xml-id-20050909"><cite>xml:id Version 1.0.</cite></a> 9 September 2005. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2005/REC-xml-id-20050909">http://www.w3.org/TR/2005/REC-xml-id-20050909</a>