Ed Summers; Antoine Isaac. <a href="http://www.w3.org/TR/2009/WD-skos-primer-20090317"><cite>SKOS Simple Knowledge Organization System Primer.</cite></a> 17 March 2009. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2009/WD-skos-primer-20090317">http://www.w3.org/TR/2009/WD-skos-primer-20090317</a>