@article{DAN_1987_295_6_a2,
     author = {S. M. Grudskii},
     title = {Factorization of $u$-periodic matrix-functions and problems with},
     journal = {Doklady Akademii Nauk},
     pages = {1298--1302},
     year = {1987},
     volume = {295},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1987_295_6_a2/}
}