@article{DE_1979_15_4_a21,
     author = {R. R. Mkrtumyan},
     title = {A fourth-order linear equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {740--742},
     publisher = {mathdoc},
     volume = {15},
     number = {4},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1979_15_4_a21/}
}