@article{DE_2006_42_9_a1,
     author = {A. I. Kozhanov and L. S. Pulkina},
     title = {On the solvability of boundary value problems with a nonlocal boundary condition of integral form for multidimensional hyperbolic equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1166--1179},
     publisher = {mathdoc},
     volume = {42},
     number = {9},
     year = {2006},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_2006_42_9_a1/}
}