@article{13153,
  author = {Ola Elvetun and Bj{\o}rn Nielsen},
  title = {PDE-constrained optimization with local control and boundary observations: Robust preconditioners},
  year = {2016},
  journal = {SIAM Journal on Scientific Computing},
  volume = {38},
  pages = {A3461-A3491},
  publisher = {Society for Industrial and Applied Mathematics},
  doi = {10.1137/140999098},
}