@article{GDZPPN002303302, title = {On the Type Number of Hypersurfaces in Spaces of Constant Curvature.}, journal = {Mathematische Annalen}, volume = {189}, year = {1970}, pages = {310-316}, zbl = {0187.19202}, url = {http://dml.mathdoc.fr/item/GDZPPN002303302} }
FERUS, D. On the Type Number of Hypersurfaces in Spaces of Constant Curvature.. Mathematische Annalen, Tome 189 (1970) pp. 310-316. http://gdmltest.u-ga.fr/item/GDZPPN002303302/