@Misc{ 
  Par21,
  author = { Paronetto, Fabio },
  title = { Two generalized Tricomi equations },
  journal = { Calc. Var. Partial Differential Equations },
  year = { 2021 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/4856/ },
  note = { cvgmt preprint}
}