@Article{ 
  balmon,
  author = { Balogh, Zoltan and Monti, Roberto },
  title = { Accessible domains in the Heisenberg group },
  journal = { Proc. Amer. Math. Soc.  },
  year = { 2004 },
  volume = { 132 },
  pages = { 97-106 },
  URL = { http://cvgmt.sns.it/paper/906/ },
  note = { cvgmt preprint}
}