@article{CMH_1994__69_4_140324,
     author = {Gilbert Levitt},
     title = {Graphs of actions on {R-trees.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {28--38},
     publisher = {mathdoc},
     volume = {69},
     number = {4},
     year = {1994},
     zbl = {0802.05044},
     url = {http://geodesic.mathdoc.fr/item/CMH_1994__69_4_140324/}
}