@Article{ 
  GenSar13,
  author = { Gentili, Graziano and Sarfatti, Giulia },
  title = { Landau-Toeplitz theorems for slice regular functions over quaternions },
  journal = { Pacific J. Math. },
  year = { 2013 },
  doi = { 10.2140/pjm.2013.265.381 },
  volume = { 265 },
  number = { 2 },
  pages = { 381-404 },
  URL = { https://gecogedi.dimai.unifi.it/paper/121/ },
  note = { cvgmt preprint}
}