Jörg Bauer Tobe Toben Bernd Westphal Mind the Shapes: Abstraction Refinement Via Topology Invariants. 35-50 2007 conf/atva/2007 ATVA http://dx.doi.org/10.1007/978-3-540-75596-8_5 db/conf/atva/atva2007.html#BauerTW07