@Misc{ 
  Ste20,
  author = { Stefani, Giorgio },
  title = { A Distributional Approach to Fractional Sobolev Spaces and Fractional Variation },
  journal = {  },
  year = { 2020 },
  pages = { 158 },
  URL = { http://cvgmt.sns.it/paper/4678/ },
  note = { cvgmt preprint}
}