@article{10_4171_ifb_223,
     author = {Tuomo Valkonen},
     title = {Optimal transportation networks and stations},
     journal = {Interfaces and free boundaries},
     pages = {569--597},
     year = {2009},
     volume = {11},
     number = {4},
     doi = {10.4171/ifb/223},
     url = {http://geodesic.mathdoc.fr/articles/10.4171/ifb/223/}
}