Michael Kay. <a href="http://www.w3.org/TR/2007/REC-xslt20-20070123"><cite>XSL Transformations (XSLT) Version 2.0.</cite></a> 23 January 2007. W3C Recommendation. URL: <a href="http://www.w3.org/TR/2007/REC-xslt20-20070123">http://www.w3.org/TR/2007/REC-xslt20-20070123</a>