@Misc{ 
  mon07,
  author = { Monti, Roberto },
  title = { Heisenberg isoperimetric problem. The axial case },
  journal = { Adv. Calc. Var.  },
  year = { 2008 },
  volume = { 1 },
  number = { 1 },
  pages = { 93-121 },
  URL = { http://cvgmt.sns.it/paper/191/ },
  note = { cvgmt preprint}
}