@article{DAN_1971_198_2_a5,
     author = {V. Ya. Ivrii},
     title = {Differential equations, with multiple characteristics, that have no solutions},
     journal = {Doklady Akademii Nauk},
     pages = {279--282},
     publisher = {mathdoc},
     volume = {198},
     number = {2},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_198_2_a5/}
}