@Misc{ 
  CapLeD13,
  author = { Capogna, Luca and Le Donne, Enrico },
  title = { Smoothness of subRiemannian isometries },
  journal = {  },
  year = { 2013 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/4162/ },
  note = { cvgmt preprint}
}