@article{02142909, title = {A group-free characterization of the }, journal = {Advances in Geometry}, volume = {4}, year = {2004}, pages = {141-164}, doi = {10.1515/advg.2004.011}, zbl = {1068.51007}, language = {en}, url = {http://dml.mathdoc.fr/item/02142909} }
Cooperstein, Bruce N.; Shpectorov, Sergey V. A group-free characterization of the . Advances in Geometry, Tome 4 (2004) pp. 141-164. doi : 10.1515/advg.2004.011. http://gdmltest.u-ga.fr/item/02142909/