@article{DE_1999_35_6_a19,
     author = {A. G. Nikitin and A. P. Petrov},
     title = {Passage to the limit with respect to a small parameter for the eigenvalues of a singularly perturbed {Sturm--Liouville} problem},
     journal = {Differencialʹnye uravneni\^a},
     pages = {843--845},
     publisher = {mathdoc},
     volume = {35},
     number = {6},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1999_35_6_a19/}
}