@article{DE_1990_26_5_a22,
     author = {V. I. Gu\c{t}u},
     title = {Periodic solutions of one-dimensional and two-dimensional systems of differential equations with impulses},
     journal = {Differencialʹnye uravneni\^a},
     pages = {904--906},
     publisher = {mathdoc},
     volume = {26},
     number = {5},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1990_26_5_a22/}
}