Harry Halpin; Ian Davis. <a href="http://www.w3.org/TR/2007/NOTE-grddl-primer-20070628"><cite>GRDDL Primer.</cite></a> 28 June 2007. W3C Note. URL: <a href="http://www.w3.org/TR/2007/NOTE-grddl-primer-20070628">http://www.w3.org/TR/2007/NOTE-grddl-primer-20070628</a>