@misc{BorndoerferErolGraffagninoetal.2012, author = {Ralf Bornd{\"o}rfer and Berkan Erol and Thomas Graffagnino and Thomas Schlechte and Elmar Swarat}, title = {Aggregation Methods for Railway Networks}, institution = {Research Center Matheon}, type = {preprintmatheon}, year = {2012}, }