@article{DAN_1962_144_4_a4,
     author = {V. P. Didenko},
     title = {Some systems of differential equations of mixed type},
     journal = {Doklady Akademii Nauk},
     pages = {709--712},
     year = {1962},
     volume = {144},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1962_144_4_a4/}
}