@Misc{ 
  donnicduy02a,
  author = { Danielli, Donatella and Garofalo, Nicola and Nhieu, Duy-Minh },
  title = { Notions of convexity in Carnot groups },
  journal = { Communications in Analysis and Geometry },
  year = { 2002 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/1634/ },
  note = { cvgmt preprint}
}