@techreport{BornemannErdmannKornhuber1993, author = {Folkmar A. Bornemann and Bodo Erdmann and Ralf Kornhuber}, title = {A Posteriori Error Estimates for Elliptic Problems.}, institution = {ZIB}, address = {Takustr. 7, 14195 Berlin}, number = {SC-93-29}, language = {eng}, year = {1993} }