Thomas Bittner Maureen Donnelly Barry Smith Endurants and perdurants in directly depicting ontologies. 247-258 2004 17 AI Commun. 4 http://iospress.metapress.com/openurl.asp?genre=article&issn=0921-7126&volume=17&issue=4&spage=247 db/journals/aicom/aicom17.html#BittnerDS04