@Misc{ 
  fraserser06,
  author = { Franchi, Bruno and Serapioni, Raul and Serra Cassano, Francesco },
  title = { Intrinsic Lipshitz graphs in Heisenebrg groups },
  journal = { J. Nonlinear and Convex Analysis },
  year = { 2006 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/68/ },
  note = { cvgmt preprint}
}