@Article{ 
  san,
  author = { Santambrogio, Filippo },
  title = { Optimal Channel Networks, Landscape Function and Branched Transport },
  journal = { Interfaces and Free Boundaries },
  year = { 2007 },
  volume = { 9 },
  pages = { 149-169 },
  URL = { http://cvgmt.sns.it/paper/1101/ },
  note = { cvgmt preprint}
}