@Misc{ 
  Mon13a,
  author = { Mondino, Andrea },
  title = { A new notion of angle between three points in a metric space },
  journal = { Crelle's Journal },
  year = { 2013 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/2085/ },
  note = { cvgmt preprint}
}