@Misc{ 
  dangarnhi,
  author = { Danielli, Donatella and Garofalo, Nicola and Nhieu, Duy-Minh },
  title = { On the best possible character of the $L^Q$ norm in some a priori estimates for non-divergence form equations in Carnot groups },
  journal = { Proc. of the Amer. Math. Soc. },
  year = { 2002 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/956/ },
  note = { cvgmt preprint}
}