@Article{ 
  santil04,
  author = { Santambrogio, Filippo and Tilli, Paolo },
  title = { Blow-up of Optimal Sets in the Irrigation Problem },
  journal = { J. Geom. Anal. },
  year = { 2005 },
  volume = { 15 },
  number = { 2 },
  pages = { 343-362 },
  URL = { http://cvgmt.sns.it/paper/531/ },
  note = { cvgmt preprint}
}