@article{DE_1980_16_9_a1,
     author = {A. B. Budak},
     title = {Expansion in eigenfunctions of a fourth-order differential operator with a piecewise constant leading coefficient},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1545--1558},
     publisher = {mathdoc},
     volume = {16},
     number = {9},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1980_16_9_a1/}
}