@article{DE_1972_8_4_a6,
     author = {G. S. Yudaev},
     title = {Certain questions of the instability of systems with aftereffect},
     journal = {Differencialʹnye uravneni\^a},
     pages = {633--638},
     publisher = {mathdoc},
     volume = {8},
     number = {4},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1972_8_4_a6/}
}