@Article{ 
  fraserser02,
  author = { Franchi, Bruno and Serapioni, Raul and Serra Cassano, Francesco },
  title = { Rectifiability and perimeter in step 2 groups },
  journal = { Mathematica Bohemica },
  year = { 2002 },
  volume = { 127 },
  number = { 2 },
  pages = { 219-228 },
  URL = { http://cvgmt.sns.it/paper/471/ },
  note = { cvgmt preprint}
}