@article{DE_1987_23_3_a4,
     author = {\`E. I. Grudo and A. K. Demenchuk},
     title = {On periodic solutions with incommensurable periods of linear inhomogeneous periodic differential systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {409--416},
     publisher = {mathdoc},
     volume = {23},
     number = {3},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1987_23_3_a4/}
}