@article{DAN_1983_270_3_a9,
     author = {P. E. Sobolevskii and S. M. Semenov},
     title = {On an approach to the investigation of degenerate hyperbolic equations},
     journal = {Doklady Akademii Nauk},
     pages = {555--558},
     publisher = {mathdoc},
     volume = {270},
     number = {3},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1983_270_3_a9/}
}