@article{RM_1972_27_5_a21,
     author = {O. A. Oleinik and E. V. Radkevich},
     title = {Systems of differential equations that have nonanalytic solutions},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     publisher = {mathdoc},
     volume = {27},
     number = {5},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1972_27_5_a21/}
}