Alexander Ferrein Stefan Schiffer 0002 Gerhard Lakemeyer A Fuzzy Set Semantics for Qualitative Fluents in the Situation Calculus. 498-509 2008 ICIRA (1) http://dx.doi.org/10.1007/978-3-540-88513-9_54 conf/icira/2008-1 db/conf/icira/icira2008-1.html#FerreinSL08