@article{DE_1973_9_2_a12,
     author = {L. A. Kotko},
     title = {The behavior of the eigenfunctions and eigenvalues of elliptic boundary value problems under variation of the domain},
     journal = {Differencialʹnye uravneni\^a},
     pages = {307--319},
     publisher = {mathdoc},
     volume = {9},
     number = {2},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_2_a12/}
}