@Misc{ 
  arecar08,
  author = { Arena, Gabriella and Caruso, Andrea Orazio },
  title = { "Higher order calculus on step two Carnot groups and applications" },
  journal = {  },
  year = { 2009 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/964/ },
  note = { cvgmt preprint}
}