@article{DE_1990_26_9_a1,
     author = {R. Sh. Bakuradze and I. V. Stankevich},
     title = {Some identities for eigenvalues and eigenfunctions of a class of fourth-order differential operators},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1483--1490},
     publisher = {mathdoc},
     volume = {26},
     number = {9},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1990_26_9_a1/}
}