Shane McCarron. <a href="http://www.w3.org/TR/2009/NOTE-xhtml-media-types-20090116"><cite>XHTML Media Types - Second Edition.</cite></a> 16 January 2009. W3C Note. URL: <a href="http://www.w3.org/TR/2009/NOTE-xhtml-media-types-20090116">http://www.w3.org/TR/2009/NOTE-xhtml-media-types-20090116</a>