@article{DE_1987_23_8_a9,
     author = {L. Tepoyan},
     title = {Fourth-order degenerate operator-differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1366--1376},
     publisher = {mathdoc},
     volume = {23},
     number = {8},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1987_23_8_a9/}
}