@Misc{ 
  Ger16,
  author = { Geraci, Francesco },
  title = { The Classical Obstacle problem with coefficients in fractional Sobolev spaces },
  journal = { Annali di Matematica Pura ed Applicata },
  year = { 2017 },
  doi = { DOI: 10.1007/s10231-017-0692-x },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3045/ },
  note = { cvgmt preprint}
}