@article{DE_1978_14_3_a18,
     author = {N. G. Bulgakov},
     title = {On the question of the stability of the solutions of second order systems in critical cases},
     journal = {Differencialʹnye uravneni\^a},
     pages = {543--545},
     publisher = {mathdoc},
     volume = {14},
     number = {3},
     year = {1978},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1978_14_3_a18/}
}