@article{DAN_1975_221_6_a1,
     author = {V. Ya. Ivrii},
     title = {Conditions that the {Cauchy} problem for hyperbolic operators with characteristics of variable multiplicity be well posed in {Gevrey} classes},
     journal = {Doklady Akademii Nauk},
     pages = {1253--1255},
     publisher = {mathdoc},
     volume = {221},
     number = {6},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1975_221_6_a1/}
}