@Article{ 
  monmora,
  author = { Monti, Roberto and Morbidelli, Daniele },
  title = { Trace theorems for vector fields },
  journal = { Math. Z. },
  year = { 2003 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/200/ },
  note = { cvgmt preprint}
}