@article{1077467776,
author = {Calabi, E.},
title = {An extension of E. Hopf's maximum principle with an application to Riemannian geometry},
journal = {Duke Math. J.},
volume = {25},
number = {1},
year = {1958},
pages = { 45-56},
language = {en},
url = {http://dml.mathdoc.fr/item/1077467776}
}
Calabi, E. An extension of E. Hopf’s maximum principle with an application to Riemannian geometry. Duke Math. J., Tome 25 (1958) no. 1, pp. 45-56. http://gdmltest.u-ga.fr/item/1077467776/