@article{DE_1972_8_2_a15,
     author = {V. S. Ryzhii},
     title = {The uniqueness of a solution of the {Cauchy} problem for second order equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {349--361},
     publisher = {mathdoc},
     volume = {8},
     number = {2},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1972_8_2_a15/}
}