Nicolas Bousquet Jean Daligault Stéphan Thomassé Anders Yeo A Polynomial Kernel for Multicut in Trees. 183-194 2009 STACS http://drops.dagstuhl.de/opus/volltexte/2009/1824 conf/stacs/2009 db/conf/stacs/stacs2009.html#BousquetDTY09