Steven J. DeRose. <a href="http://www.w3.org/TR/1999/NOTE-xptr-req-19990224"><cite>XML XPointer Requirements Version 1.0.</cite></a> 24 February 1999. W3C Note. URL: <a href="http://www.w3.org/TR/1999/NOTE-xptr-req-19990224">http://www.w3.org/TR/1999/NOTE-xptr-req-19990224</a>