@Article{ 
  Sar15,
  author = { Sarfatti, Giulia },
  title = { Quaternionic Hankel operators and approximation by slice regular
  functions },
  journal = { Indiana U. Math. J. },
  year = { 2016 },
  doi = { 10.1512/iumj.2016.65.5896 },
  volume = { 65 },
  number = { 5 },
  pages = { 1735–1757 },
  URL = { https://gecogedi.dimai.unifi.it/paper/127/ },
  note = { cvgmt preprint}
}