Feng Pan; Jerry R. Hobbs. <a href="http://www.w3.org/TR/2006/WD-owl-time-20060927"><cite>Time Ontology in OWL.</cite></a> 27 September 2006. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2006/WD-owl-time-20060927">http://www.w3.org/TR/2006/WD-owl-time-20060927</a>