@Article{ 
  Mag4,
  author = { Magnani, Valentino },
  title = { Note on coarea formulae in the Heisenberg group  },
  journal = { Publ. Mat. },
  year = { 2004 },
  volume = { 48 },
  number = { 2 },
  pages = { 409-422 },
  URL = { http://cvgmt.sns.it/paper/1729/ },
  note = { cvgmt preprint}
}