@article{GDZPPN002280043, title = {\"Uber isotrope Mannigfaltigkeiten}, journal = {Mathematische Annalen}, volume = {116}, year = {1939}, pages = {297-309}, zbl = {65.0757.01}, url = {http://dml.mathdoc.fr/item/GDZPPN002280043} }
Lense, J. Über isotrope Mannigfaltigkeiten. Mathematische Annalen, Tome 116 (1939) pp. 297-309. http://gdmltest.u-ga.fr/item/GDZPPN002280043/