@article{DAN_1972_207_4_a4,
     author = {O. A. Oleinik and E. V. Radkevich},
     title = {Analyticity of solutions of linear differential equations and systems},
     journal = {Doklady Akademii Nauk},
     pages = {785--788},
     publisher = {mathdoc},
     volume = {207},
     number = {4},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1972_207_4_a4/}
}