@article{DE_1989_25_2_a6,
     author = {V. S. Mokeichev},
     title = {Eigenvalues of boundary value problems. {Transformations} of boundary value problems to boundary value problems with small coefficients},
     journal = {Differencialʹnye uravneni\^a},
     pages = {222--228},
     publisher = {mathdoc},
     volume = {25},
     number = {2},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1989_25_2_a6/}
}