Steven Schockaert Jeroen Janssen Dirk Vermeir Martine De Cock Answer Sets in a Fuzzy Equilibrium Logic. 135-149 2009 RR http://dx.doi.org/10.1007/978-3-642-05082-4_10 conf/rr/2009 db/conf/rr/rr2009.html#SchockaertJVC09