@techreport{BodlaenderKosterWolle2004, author = {Hans L. Bodlaender and Arie M.C.A. Koster and Thomas Wolle}, title = {Contraction and Treewidth Lower Bounds}, institution = {ZIB}, address = {Takustr. 7, 14195 Berlin}, number = {04-29}, language = {eng}, year = {2004} }