Frithjof Dau Peter W. Eklund A Diagrammatic Reasoning System for <i>ALC</i>. 39-51 2007 conf/ksem/2007 KSEM http://dx.doi.org/10.1007/978-3-540-76719-0_8 db/conf/ksem/ksem2007.html#DauE07