@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}
}