@article{GDZPPN002289555, title = {Hyperbolic surfaces of the form z == f (x, y).}, journal = {Mathematische Annalen}, volume = {142}, year = {1961}, pages = {77-79}, zbl = {0124.29103}, url = {http://dml.mathdoc.fr/item/GDZPPN002289555} }
OSSERMAN, R. Hyperbolic surfaces of the form z == f (x, y).. Mathematische Annalen, Tome 142 (1961) pp. 77-79. http://gdmltest.u-ga.fr/item/GDZPPN002289555/