@article{MZ_1988__200_3_174009,
     author = {Wolfgang Walter},
     title = {A {Theorem} on {Elliptic} {Differential} {Inequalities} with an {Application} to {Gradient} {Bounds.}},
     journal = {Mathematische Zeitschrift},
     pages = {293--300},
     publisher = {mathdoc},
     volume = {200},
     number = {3},
     year = {1988},
     zbl = {0646.35034},
     url = {http://geodesic.mathdoc.fr/item/MZ_1988__200_3_174009/}
}