@Misc{ 
  Spe15,
  author = { Spector, Daniel },
  title = { On a generalization of $L^p$-differentiability },
  journal = {  },
  year = { 2015 },
  pages = { 22 },
  URL = { http://cvgmt.sns.it/paper/2820/ },
  note = { cvgmt preprint}
}