@article{DAN_1971_198_2_a0,
     author = {Yu. N. Valitskii},
     title = {On the convergence of difference approximations of the eigenvalues and eigenfunctions of a two-dimensional elliptic operator},
     journal = {Doklady Akademii Nauk},
     pages = {263--265},
     publisher = {mathdoc},
     volume = {198},
     number = {2},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_198_2_a0/}
}