A. Dreweke Marc Wörlein Ingrid Fischer D. Schell Thorsten Meinl Michael Philippsen Graph-Based Procedural Abstraction. 259-270 2007 conf/cgo/2007 CGO http://doi.ieeecomputersociety.org/10.1109/CGO.2007.14 db/conf/cgo/cgo2007.html#DrewekeWFSMP07