@article{DAN_1973_209_4_a10,
     author = {V. M. Petkov},
     title = {On the {Cauchy} problem for first-order hyperbolic systems with multiple characteristics},
     journal = {Doklady Akademii Nauk},
     pages = {795--797},
     publisher = {mathdoc},
     volume = {209},
     number = {4},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1973_209_4_a10/}
}