@article{MZ_1995__218_4_174749,
     author = {Michael Wolf},
     title = {Harmonic maps form surfaces to {R-trees.}},
     journal = {Mathematische Zeitschrift},
     pages = {577--594},
     publisher = {mathdoc},
     volume = {218},
     number = {4},
     year = {1995},
     zbl = {0827.58011},
     url = {http://geodesic.mathdoc.fr/item/MZ_1995__218_4_174749/}
}