@article{DAN_1972_207_5_a2,
     author = {V. Ya. Ivrii},
     title = {Cauchy problem for nonstrictly hyperbolic equations},
     journal = {Doklady Akademii Nauk},
     pages = {1032--1034},
     publisher = {mathdoc},
     volume = {207},
     number = {5},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1972_207_5_a2/}
}