@article{IM_1994__116_1-3_144196,
     author = {M.A. Ronan and J. Tits},
     title = {Twin trees {I.}},
     journal = {Inventiones mathematicae},
     pages = {463--480},
     publisher = {mathdoc},
     volume = {116},
     number = {1-3},
     year = {1994},
     zbl = {0839.20045},
     url = {http://geodesic.mathdoc.fr/item/IM_1994__116_1-3_144196/}
}