@article{DE_1968_4_9_a3,
     author = {V. P. Glushko},
     title = {Degenerate linear differential equations. {I}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1584--1597},
     publisher = {mathdoc},
     volume = {4},
     number = {9},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1968_4_9_a3/}
}