@Article{ 
  FocSpa17,
  author = { Focardi, Matteo and Spadaro, Emanuele },
  title = { On the measure and the structure of the free boundary  of the lower dimensional obstacle problem },
  journal = { Archive for Rational Mechanics and Analysis },
  year = { 2018 },
  volume = { 230 },
  pages = { 125--184 },
  URL = { http://cvgmt.sns.it/paper/3356/ },
  note = { cvgmt preprint}
}