@article{DAN_1964_158_6_a6,
     author = {T. I. Zelenyak},
     title = {A mixed problem for an equation which cannot be solved for the highest-order time derivative},
     journal = {Doklady Akademii Nauk},
     pages = {1268--1270},
     publisher = {mathdoc},
     volume = {158},
     number = {6},
     year = {1964},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1964_158_6_a6/}
}