Assaf Natanzon Ron Shamir Roded Sharan A Polynomial Approximation Algorithm for the Minimum Fill-In Problem. 1067-1079 2000 30 SIAM J. Comput. 4 http://epubs.siam.org/sam-bin/dbq/article/33607 db/journals/siamcomp/siamcomp30.html#NatanzonSS00