@Article{ 
  BuGeRuVe13,
  author = { Buttazzo, Giuseppe and Gerolin, Augusto and Ruffini, Berardo and Velichkov, Bozhidar },
  title = { Optimal Potentials for Schrödinger Operators },
  journal = { J. Éc. polytech. Math. },
  year = { 2013 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/2140/ },
  note = { cvgmt preprint}
}