@article{DE_1971_7_9_a13,
     author = {P. K. Senatorov},
     title = {The stability of the system of eigenvalues and eigenfunctions of the {Sturm--Liouville} problem},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1667--1671},
     publisher = {mathdoc},
     volume = {7},
     number = {9},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1971_7_9_a13/}
}