@Misc{ 
  Cat11a,
  author = { Catino, Giovanni },
  title = { A note on four dimensional (anti-)self-dual quasi-Einstein manifolds },
  journal = {  },
  year = { 2011 },
  pages = {  },
  URL = { https://gecogedi.dimai.unifi.it/paper/539/ },
  note = { cvgmt preprint}
}