@Misc{ 
  FerMerCha16,
  author = { Chambolle, Antonin and Ferrari, Luca and Merlet, Benoit },
  title = { A phase-field approximation for the Steiner problem in dimension two },
  journal = { Advances in Calculus of Variations },
  year = { 2017 },
  doi = { 10.1515/acv-2016-0034 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3337/ },
  note = { cvgmt preprint}
}