@techreport{Griebel:1987,
author = {M.~Griebel},
title = { On the combination of the ideas of multilevel solvers
using hierarchical bases and the substructuring technique
for the finite element method},
institution = {{Bericht} {I8709}, Institut f\"ur Informatik, TU M\"unchen},
year = {1987},
annote = {report}
}