Marc Denecker Joost Vennekens Well-Founded Semantics and the Algebraic Theory of Non-monotone Inductive Definitions. 84-96 2007 conf/lpnmr/2007 LPNMR http://dx.doi.org/10.1007/978-3-540-72200-7_9 db/conf/lpnmr/lpnmr2007.html#DeneckerV07