Glencora Borradaile Erik D. Demaine Siamak Tazari Polynomial-Time Approximation Schemes for Subset-Connectivity Problems in Bounded-Genus Graphs. 171-182 2009 STACS http://drops.dagstuhl.de/opus/volltexte/2009/1835 conf/stacs/2009 db/conf/stacs/stacs2009.html#BorradaileDT09