@article{DE_1981_17_12_a1,
     author = {V. Ya. Derr},
     title = {On the question of factorization of a linear boundary value problem},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2123--2135},
     publisher = {mathdoc},
     volume = {17},
     number = {12},
     year = {1981},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1981_17_12_a1/}
}