@Article{ 
  Fto20,
  author = { Ftouhi, Ilias },
  title = { Where to place a spherical obstacle so as to maximize the  first Steklov eigenvalue ? },
  journal = { ESAIM Control and Calculus of Variations },
  year = { 2021 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/5201/ },
  note = { cvgmt preprint}
}