@article{DE_1969_5_4_a4,
     author = {Yu. I. Lyubich and V. A. Tkachenko},
     title = {On a {Floquet} theory for equations with retarded argument},
     journal = {Differencialʹnye uravneni\^a},
     pages = {648--656},
     publisher = {mathdoc},
     volume = {5},
     number = {4},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1969_5_4_a4/}
}