@Misc{ 
  Car20,
  author = { Carbotti, Alessandro },
  title = { Approximation properties of solutions to fractional equations, Riemann-Liouville fractional Sobolev spaces and a variational problem in Carnot Groups. },
  journal = {  },
  year = { 2020 },
  pages = { 138 },
  URL = { http://cvgmt.sns.it/paper/5087/ },
  note = { cvgmt preprint}
}