Geoff Sutcliffe The CADE-20 Automated Theorem Proving Competition. 173-181 2006 19 AI Commun. 2 http://iospress.metapress.com/openurl.asp?genre=article&issn=0921-7126&volume=19&issue=2&spage=173 db/journals/aicom/aicom19.html#Sutcliffe06