@article{10_4171_ifb_149,
     author = {Emanuele Paolini and Eugene Stepanov},
     title = {Optimal transportation networks as flat chains},
     journal = {Interfaces and free boundaries},
     pages = {393--436},
     year = {2006},
     volume = {8},
     number = {4},
     doi = {10.4171/ifb/149},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ifb/149/}
}