@Misc{ 
  balfra,
  author = { Baldi, Annalisa and Franchi, Bruno },
  title = { Differential forms in Carnot groups: a Gamma-convergence approach },
  journal = { Calc. Var. Partial Differential Equations },
  year = { 2010 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/1450/ },
  note = { cvgmt preprint}
}