@Article{ 
  alcslapr,
  author = { Alberti, Giovanni and Csörnyei, Marianna and Laczkovich, Miklós and Preiss, David },
  title = { Denjoy-Young-Saks theorem for approximate derivatives revisited },
  journal = { Real Anal. Exchange },
  year = { 2000 },
  volume = { 26 (2000/01) },
  number = { 1 },
  pages = { 485-488 },
  URL = { http://cvgmt.sns.it/paper/1159/ },
  note = { cvgmt preprint}
}