@Techreport{surevetter2004opcu, author = "York Sure-Vetter and Jens Hartmann and Robert Meersman and Peter Spyns and Andriy Lisovoy and Rudi Studer", institution = "Institute AIFB, University of Karlsruhe", number = "6.5", title = "OntoWeb Portal: Content Upkeep", year = "2004", }