@Article{ 
  LeDMag10,
  author = { Le Donne, Enrico and Magnani, Valentino },
  title = { Measure of submanifolds in the Engel group },
  journal = { Rev. Mat. Iberoam. },
  year = { 2010 },
  volume = { 26 },
  number = { 1 },
  pages = { 333–346 },
  URL = { http://cvgmt.sns.it/paper/2171/ },
  note = { cvgmt preprint}
}