@Article{ 
  PreSpe13,
  author = { Preiss, David and Speight, Gareth },
  title = { Differentiability of Lipschitz Functions in Lebesgue Null Sets },
  journal = { Inventiones Mathematicae },
  year = { 2013 },
  volume = { 199 },
  number = { 2 },
  pages = { 517-559 },
  URL = { http://cvgmt.sns.it/paper/3436/ },
  note = { cvgmt preprint}
}