@article{DE_1997_33_4_a23,
     author = {Yang Guang-wu and Xu Ke-ming},
     title = {Uniqueness and stability of the solution of a problem with a directional derivative for a second-order equation of elliptic type},
     journal = {Differencialʹnye uravneni\^a},
     pages = {570--572},
     publisher = {mathdoc},
     volume = {33},
     number = {4},
     year = {1997},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1997_33_4_a23/}
}