@article{DE_2000_36_4_a20,
     author = {E. M. Karchevskii and S. I. Solov'ev},
     title = {Investigation of a spectral problem for the {Helmholtz} operator on the plane},
     journal = {Differencialʹnye uravneni\^a},
     pages = {563--565},
     publisher = {mathdoc},
     volume = {36},
     number = {4},
     year = {2000},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_2000_36_4_a20/}
}