@article{GDZPPN002321815, title = {Axial Isometries of Manifolds of Non-Positive Curvature.}, journal = {Mathematische Annalen}, volume = {261}, year = {1982}, pages = {131-144}, zbl = {0487.53039}, url = {http://dml.mathdoc.fr/item/GDZPPN002321815} }
Ballmann, Werner. Axial Isometries of Manifolds of Non-Positive Curvature.. Mathematische Annalen, Tome 261 (1982) pp. 131-144. http://gdmltest.u-ga.fr/item/GDZPPN002321815/