Owen Cliffe Marina De Vos Julian A. Padget Modelling Normative Frameworks Using Answer Set Programing. 548-553 2009 LPNMR http://dx.doi.org/10.1007/978-3-642-04238-6_56 conf/lpnmr/2009 db/conf/lpnmr/lpnmr2009.html#CliffeVP09