@Misc{ 
  Cat18,
  author = { Catino, Giovanni },
  title = { Rigidity of positively curved shrinking Ricci solitons in dimension four },
  journal = { Geom. Flows },
  year = { 2018 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3948/ },
  note = { cvgmt preprint}
}