@article{GDZPPN002229870,
title = {Monotonicity of certain differential operators in divergence form.},
journal = {Manuscripta mathematica},
volume = {64},
year = {1989},
pages = {253-260},
zbl = {0718.47026},
url = {http://dml.mathdoc.fr/item/GDZPPN002229870}
}
Boccardo, L.; Dacorogna, B. Monotonicity of certain differential operators in divergence form.. Manuscripta mathematica, Tome 64 (1989) pp. 253-260. http://gdmltest.u-ga.fr/item/GDZPPN002229870/