@Misc{ 
  CatDamMas20,
  author = { Catino, Giovanni and Dameno, Davide and Mastrolia, Paolo },
  title = { On Riemannian four-manifolds and their twistor spaces: a moving frame
  approach },
  journal = {  },
  year = { 2020 },
  pages = {  },
  URL = { https://gecogedi.dimai.unifi.it/paper/515/ },
  note = { cvgmt preprint}
}