@Misc{ 
  monmor03,
  author = { Monti, Roberto and Morbidelli, Daniele },
  title = { Isoperimetric inequality in the Grushin plane },
  journal = { J. Geom. Anal. },
  year = { 2003 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/569/ },
  note = { cvgmt preprint}
}