@Article{ 
  CalFin15,
  author = { Calvaruso, Giovanni and Fino, Anna },
  title = { Four-dimensional pseudo-Riemannian homogeneous Ricci solitons },
  journal = { Int. J. Geom. Methods Mod. Phys. },
  year = { 2015 },
  doi = { 10.1142/S0219887815500565 },
  volume = { 12 },
  pages = { 1550056 },
  URL = { https://gecogedi.dimai.unifi.it/paper/181/ },
  note = { cvgmt preprint}
}