@article{DE_1987_23_7_a13,
     author = {S. I. Kovalev},
     title = {A difference method for solving a two-dimensional spectral problem in an unbounded domain},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1231--1240},
     publisher = {mathdoc},
     volume = {23},
     number = {7},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1987_23_7_a13/}
}