@article{DE_1988_24_2_a1,
     author = {A. I. Vahabov},
     title = {Nonregular pencils of differential operators in a space of vector functions},
     journal = {Differencialʹnye uravneni\^a},
     pages = {199--207},
     publisher = {mathdoc},
     volume = {24},
     number = {2},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1988_24_2_a1/}
}