@article{05237145, title = {Liouville theorems for a class of linear second-order operators with nonnegative characteristic form.}, journal = {Boundary Value Problems [electronic only]}, volume = {2007}, year = {2007}, doi = {10.1155/2007/48232}, zbl = {1158.35338}, language = {en}, url = {http://dml.mathdoc.fr/item/05237145} }
Kogoj, Alessia Elisabetta; Lanconelli, Ermanno. Liouville theorems for a class of linear second-order operators with nonnegative characteristic form.. Boundary Value Problems [electronic only], Tome 2007 (2007) . doi : 10.1155/2007/48232. http://gdmltest.u-ga.fr/item/05237145/