@article{DE_1977_13_11_a14,
     author = {A. F. Filippov},
     title = {A boundary value problem for the wave equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2043--2050},
     publisher = {mathdoc},
     volume = {13},
     number = {11},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_11_a14/}
}