@Article{ 
  mag00,
  author = { Magnani, Valentino },
  title = { Differentiability and Area formula on Stratified Lie groups },
  journal = { Houston J. Math. },
  year = { 2001 },
  volume = { 27 },
  number = { 2 },
  pages = { 297-323 },
  URL = { http://cvgmt.sns.it/paper/763/ },
  note = { cvgmt preprint}
}