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@article{MZM_1983_34_3_a10, author = {A. I. Ibragimov}, title = {Some qualitative theorems for degenerate elliptic equations}, journal = {Matemati\v{c}eskie zametki}, pages = {407--416}, publisher = {mathdoc}, volume = {34}, number = {3}, year = {1983}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1983_34_3_a10/} }
A. I. Ibragimov. Some qualitative theorems for degenerate elliptic equations. Matematičeskie zametki, Tome 34 (1983) no. 3, pp. 407-416. http://geodesic.mathdoc.fr/item/MZM_1983_34_3_a10/