@article{DE_1988_24_10_a5,
     author = {V. N. Laptinskii and S. V. Podolyan},
     title = {Periodic solutions of an $n$th order vector differential equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1704--1709},
     publisher = {mathdoc},
     volume = {24},
     number = {10},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1988_24_10_a5/}
}