@Article{	  Engel.Griebel:2011,
  author	= {M.~Engel and M.~Griebel},
  title		= {{A multigrid method for constrained optimal control
		  problems}},
  journal	= {Journal of Computational and Applied Mathematics},
  pdf		= {http://wissrech.ins.uni-bonn.de/research/pub/engel/engelgriebel_r2.pdf}
		  ,
  http		= {http://dx.doi.org/10.1016/j.cam.2011.04.002},
  doi		= {10.1016/j.cam.2011.04.002},
  annote	= {article},
  volume	= {235},
  number	= {15},
  pages		= {4368 - 4388},
  year		= {2011},
  issn		= {0377-0427},
  personid	= 3,
  keywords	= {Primal-dual active set methods}
}