@Article{ 
  ButVel17,
  author = { Buttazzo, Giuseppe and Velichkov, Bozhidar },
  title = { A Shape Optimal Control Problem with Changing Sign Data },
  journal = { SIAM J. Math. Anal. },
  year = { 2018 },
  doi = { https://doi.org/10.1137/17M1126564 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3403/ },
  note = { cvgmt preprint}
}