@article {MR3094615,
    AUTHOR = {Gon{\c{c}}alves, Etereldes and Sarkis, Marcus},
     TITLE = {Analysis of robust parameter-free multilevel methods for
              {N}eumann boundary control problems},
   JOURNAL = {Comput. Methods Appl. Math.},
  FJOURNAL = {Computational Methods in Applied Mathematics},
    VOLUME = {13},
      YEAR = {2013},
    NUMBER = {2},
     PAGES = {207--235},
      ISSN = {1609-4840},
   MRCLASS = {49M25 (49K20 65N30)},
  MRNUMBER = {3094615},
       DOI = {10.1515/cmam-2013-0001},
       URL = {http://dx.doi.org/10.1515/cmam-2013-0001},
}