@techreport{BraessDeuflhardLipnikov1999, author = {Dietrich Braess and Peter Deuflhard and Konstantin Lipnikov}, title = {A Subspace Cascadic Multigrid Method for Mortar Elements}, institution = {ZIB}, address = {Takustr. 7, 14195 Berlin}, number = {SC-99-07}, language = {eng}, year = {1999} }