@Misc{ 
  Afe19,
  author = { Afeltra, Claudio },
  title = { Singular periodic solutions to a critical equation in the Heisenberg group },
  journal = {  },
  year = { 2019 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/4433/ },
  note = { cvgmt preprint}
}