Hans L. Bodlaender Ton Kloks Dieter Kratsch Treewidth and Pathwidth of Permutation Graphs. 114-125 1993 conf/icalp/1993 ICALP db/conf/icalp/icalp93.html#BodlaenderKK93 http://dx.doi.org/10.1007/3-540-56939-1_66