@article{DE_1973_9_10_a16,
     author = {A. M. Samoilenko and D. I. Martynyuk and N. A. Perestyuk},
     title = {Existence of invariant tori for systems of difference equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1904--1910},
     publisher = {mathdoc},
     volume = {9},
     number = {10},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_10_a16/}
}