@Article{ 
  delwes,
  author = { De Lellis, Camillo and Westdickenberg, Michael },
  title = { On the Optimality of Velocity Averaging Lemmas },
  journal = { Ann. Inst. Henry Poincaré Analise Non linéaire },
  year = { 2002 },
  volume = { 20 },
  pages = { 1075-1085 },
  URL = { http://cvgmt.sns.it/paper/601/ },
  note = { cvgmt preprint}
}