@Misc{ 
  LeDZüs12,
  author = { Le Donne, Enrico and Züst, Roger },
  title = { Some properties of Hölder surfaces in the Heisenberg group },
  journal = {  },
  year = { 2012 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/4164/ },
  note = { cvgmt preprint}
}