Donguk Kim Changhee Lee Youngsong Cho Deok-Soo Kim Manifoldization of pi-Shapes by Topology Operators. 505-511 2008 GMP http://dx.doi.org/10.1007/978-3-540-79246-8_40 conf/gmp/2008 db/conf/gmp/gmp2008.html#KimLCK08