Stephan Grimm Pascal Hitzler A Preferential Tableaux Calculus for Circumscriptive <i>A</i><i>LCO</i>{\mathcal ALCO}. 40-54 2009 RR http://dx.doi.org/10.1007/978-3-642-05082-4_4 conf/rr/2009 db/conf/rr/rr2009.html#GrimmH09