@Article{ 
  ButMaeVel17,
  author = { Buttazzo, Giuseppe and Maestre, Faustino and Velichkov, Bozhidar },
  title = { Optimal potentials for problems with changing sign data },
  journal = { Journal of Optimization Theory and Applications },
  year = { 2017 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3633/ },
  note = { cvgmt preprint}
}