@techreport{TorresTorresBorndoerferetal.2008, author = {Luis Miguel Torres and Ramiro Torres and Ralf Bornd{\"o}rfer and Marc Pfetsch}, title = {On the Line Planning Problem in Tree Networks}, institution = {ZIB}, address = {Takustr. 7, 14195 Berlin}, number = {08-52}, language = {eng}, year = {2008} }