@article{1183497768,
author = {Beckenbach, E. F.},
title = {A characteristic property of surfaces of negative curvature},
journal = {Bull. Amer. Math. Soc.},
volume = {40},
number = {12},
year = {1934},
pages = { 761-768},
language = {en},
url = {http://dml.mathdoc.fr/item/1183497768}
}
Beckenbach, E. F. A characteristic property of surfaces of negative curvature. Bull. Amer. Math. Soc., Tome 40 (1934) no. 12, pp. 761-768. http://gdmltest.u-ga.fr/item/1183497768/