@Article{ 
  Pic22,
  author = { Piccinini, Mirco },
  title = { The obstacle problem and the Perron Method for nonlinear fractional  equations in the Heisenberg group },
  journal = { Nonlinear Anal. },
  year = { 2022 },
  doi = { https://doi.org/10.1016/j.na.2022.112966 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/5664/ },
  note = { cvgmt preprint}
}