@article {MR2310391,
    AUTHOR = {Mathew, T. P. and Sarkis, M. and Schaerer, C. E.},
     TITLE = {Analysis of block matrix preconditioners for elliptic optimal
              control problems},
   JOURNAL = {Numer. Linear Algebra Appl.},
  FJOURNAL = {Numerical Linear Algebra with Applications},
    VOLUME = {14},
      YEAR = {2007},
    NUMBER = {4},
     PAGES = {257--279},
      ISSN = {1070-5325},
     CODEN = {NLAAEM},
   MRCLASS = {65F10 (49M25)},
  MRNUMBER = {2310391 (2008d:65038)},
MRREVIEWER = {Rafael J. Villanueva},
       DOI = {10.1002/nla.526},
       URL = {http://dx.doi.org/10.1002/nla.526},
}