Joseph Reagle Jr. <a href="http://www.w3.org/TR/1999/WD-xmldsig-requirements-19991014"><cite>XML-Signature Requirements.</cite></a> 14 October 1999. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/1999/WD-xmldsig-requirements-19991014">http://www.w3.org/TR/1999/WD-xmldsig-requirements-19991014</a>