@article{DAN_1992_324_1_a3,
     author = {P. P. Zabreiko and Nguen Van Min},
     title = {The group of characteristic operators and its applications in the theory of linear ordinary differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {24--28},
     publisher = {mathdoc},
     volume = {324},
     number = {1},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1992_324_1_a3/}
}