@article{GDZPPN002426838,
title = {Nonnegativity for the Curvature Operator and Isotropy for Isometric Immersions.},
journal = {Mathematische Zeitschrift},
volume = {180},
year = {1982},
pages = {129-142},
zbl = {0476.53032},
url = {http://dml.mathdoc.fr/item/GDZPPN002426838}
}
Walter, Rolf; Kleinjohann, Norbert. Nonnegativity for the Curvature Operator and Isotropy for Isometric Immersions.. Mathematische Zeitschrift, Tome 180 (1982) pp. 129-142. http://gdmltest.u-ga.fr/item/GDZPPN002426838/