@article{DAN_1971_201_6_a7,
     author = {G. L. Chernyshev},
     title = {On the {Friedrichs{\textendash}Lewy} inequality for $B$-hyperbolic operators},
     journal = {Doklady Akademii Nauk},
     pages = {1295--1298},
     year = {1971},
     volume = {201},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_201_6_a7/}
}