@Misc{ 
  HerSpe20,
  author = { Hernandez, Felipe and Spector, Daniel },
  title = { Fractional Integration and Optimal Estimates for Elliptic Systems },
  journal = {  },
  year = { 2020 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/4791/ },
  note = { cvgmt preprint}
}