@article{DAN_1975_224_3_a11,
     author = {\`E. M. Saak},
     title = {An estimate of the eigenvalues of an elliptic differential operator of divergence form for domains close to an ellipsoid},
     journal = {Doklady Akademii Nauk},
     pages = {543--545},
     year = {1975},
     volume = {224},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1975_224_3_a11/}
}