@article{DAN_1975_220_4_a1,
     author = {Yu. Ya. Belov},
     title = {On approximation of a class of systems of linear differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {765--768},
     year = {1975},
     volume = {220},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1975_220_4_a1/}
}