ABSTRACT
Roland Becker Hartmut Kapp Rolf Rannacher Institute of Applied M athematics University of Heidelberg INF 293, D-69120 Heidelberg, Germany r o la n d .becker@ iwr. u n i-h e id e lb e rg . de h a r tm u t.kapp@iwr.u n i-h e id e lb e rg .de rannacherQ iw r. u n i-h e id e lb e rg . de h t t p : / / g a i a . iw r . u n i-h e id e lb e rg .de
