@Article{ 
  leospe11,
  author = { Leoni, Giovanni and Spector, Daniel },
  title = { Characterization of Sobolev and BV spaces },
  journal = { Journal of Functional Analysis },
  year = { 2011 },
  volume = { 261 },
  pages = { 2926–2958 },
  URL = { http://cvgmt.sns.it/paper/1155/ },
  note = { cvgmt preprint}
}