@techreport{BorndoerferFerreiraMartin1997, author = {Ralf Bornd{\"o}rfer and Carlos E. Ferreira and Alexander Martin}, title = {Decomposing Matrices into Blocks}, institution = {ZIB}, address = {Takustr. 7, 14195 Berlin}, number = {SC-97-15}, language = {eng}, year = {1997} }