@InCollection{	  Bungartz.Griebel.Roschke.ea:1994,
  author	= {H.-J. Bungartz and M. Griebel and D. R\"oschke and C.
		  Zenger},
  title		= {Two proofs of convergence for the combination technique
		  for the efficient solution of sparse grid problems},
  editor	= {D. E. Keyes and J. Xu},
  booktitle	= {Domain Decomposition Methods in Scientific and Engineering
		  Computing, DDM7},
  address	= {Providence},
  publisher	= {American Mathematical Society},
  series	= {Contemp. Math. 180},
  pages		= {15--20},
  annote	= {series},
  year		= {1994},
  ps		= {http://wissrech.ins.uni-bonn.de/research/pub/griebel/ddm7_bgrz.ps.gz}
		  
}