@article{DAN_1967_176_6_a4,
     author = {V. N. Gol'dberg},
     title = {The occurrence of discontinuities which arise when extending solutions of nonlinear mixed problems for the string equation},
     journal = {Doklady Akademii Nauk},
     pages = {1229--1232},
     year = {1967},
     volume = {176},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1967_176_6_a4/}
}