@article{JRAM_1984__347_152602,
     author = {Robert Bieri and J.R.J. Groves},
     title = {The geometry of the set of characters iduced by valuations.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {168--195},
     publisher = {mathdoc},
     volume = {347},
     year = {1984},
     zbl = {0526.13003},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1984__347_152602/}
}