@article{DE_1992_28_5_a17,
     author = {F. E. Lomovtsev},
     title = {Necessary and sufficient conditions for the unique solvability of the {Cauchy} problem for second-order hyperbolic differential equations with a variable domain of operator coefficients},
     journal = {Differencialʹnye uravneni\^a},
     pages = {873--886},
     publisher = {mathdoc},
     volume = {28},
     number = {5},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1992_28_5_a17/}
}