Joseph Reagle. <a href="http://www.w3.org/TR/2002/NOTE-xml-encryption-req-20020304"><cite>XML Encryption Requirements.</cite></a> 4 March 2002. W3C Note. URL: <a href="http://www.w3.org/TR/2002/NOTE-xml-encryption-req-20020304">http://www.w3.org/TR/2002/NOTE-xml-encryption-req-20020304</a>