@Misc{ 
  cri07,
  author = { Crippa, Gianluca },
  title = { The flow associated to weakly differentiable vector fields },
  journal = {  },
  year = { 2007 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/655/ },
  note = { cvgmt preprint}
}