@article{DE_1978_14_9_a4,
     author = {N. A. Izobov},
     title = {Lower bound for the minimal exponent of a linear system},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1576--1588},
     publisher = {mathdoc},
     volume = {14},
     number = {9},
     year = {1978},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1978_14_9_a4/}
}