@article{BGUMI_2020_1_a3,
     author = {E. V. Ustilko and F. E. Lomovtsev},
     title = {Matching conditions for values of characteristic oblique derivative at the end of a string, initial data and right-hand side of the wave equation},
     journal = {Journal of the Belarusian State University. Mathematics and Informatics},
     pages = {30--37},
     publisher = {mathdoc},
     volume = {1},
     year = {2020},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/BGUMI_2020_1_a3/}
}