@Misc{ 
  SquVol16,
  author = { Squassina, Marco and Volzone, Bruno },
  title = { Brezis-Bourgain-Mironescu formula for magnetic operators },
  journal = { C. R. Math. Acad. Sci. Paris },
  year = { 2016 },
  volume = { 354 },
  pages = { 825-831 },
  URL = { http://cvgmt.sns.it/paper/2936/ },
  note = { cvgmt preprint}
}