@article{DE_1985_21_12_a22,
     author = {V. F. Lisyanoi},
     title = {Classification of formal periodic systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2173--2175},
     year = {1985},
     volume = {21},
     number = {12},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1985_21_12_a22/}
}