@article{TM_1934_5_a15,
     author = {S. Sobolev},
     title = {Functionally-invariant solutions of wave equation},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {259--264},
     publisher = {mathdoc},
     volume = {5},
     year = {1934},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1934_5_a15/}
}