@Misc{ 
  amb09,
  author = { Ambrosio, Luigi },
  title = { The flow associated to weakly differentiable vector fields: recent results and open problems },
  journal = {  },
  year = { 2009 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/1217/ },
  note = { cvgmt preprint}
}