@Misc{ 
  BraSal18,
  author = { Brasco, Lorenzo and Salort, Ariel },
  title = { A note on homogeneous Sobolev spaces of fractional order },
  journal = { Ann. Mat. Pura Appl. },
  year = { 2018 },
  pages = { 33 },
  URL = { http://cvgmt.sns.it/paper/3858/ },
  note = { cvgmt preprint}
}