@article{GDZPPN002186306,
title = {A metric characterization of "spherical" surfaces in n-dimensional hyperbolic space.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {247},
year = {1971},
pages = {142-152},
zbl = {0223.50014},
url = {http://dml.mathdoc.fr/item/GDZPPN002186306}
}
Valentine, Joseph E.; Andalafte, E.Z. A metric characterization of "spherical" surfaces in n-dimensional hyperbolic space.. Journal für die reine und angewandte Mathematik, Tome 247 (1971) pp. 142-152. http://gdmltest.u-ga.fr/item/GDZPPN002186306/