Fedor V. Fomin Dieter Kratsch Ioan Todinca Yngve Villanger Exact Algorithms for Treewidth and Minimum Fill-In. 1058-1079 2008 38 SIAM J. Comput. 3 http://dx.doi.org/10.1137/050643350 db/journals/siamcomp/siamcomp38.html#FominKTV08