@article{IM2_1998_62_2_a7,
     author = {S. D. Troitskaya},
     title = {A~boundary-value problem for hyperbolic equations},
     journal = {Izvestiya. Mathematics },
     pages = {399--428},
     publisher = {mathdoc},
     volume = {62},
     number = {2},
     year = {1998},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1998_62_2_a7/}
}