@Misc{ 
  LeDRig15a,
  author = { Le Donne, Enrico and Rigot, Severine },
  title = { Remarks about Besicovitch covering property in Carnot groups of step 3
  and higher },
  journal = {  },
  year = { 2015 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/4157/ },
  note = { cvgmt preprint}
}