@article{TM_1935_9_a5,
     author = {N. S. Koshlyakov},
     title = {On a second-order partial differential equations},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {189--200},
     publisher = {mathdoc},
     volume = {9},
     year = {1935},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1935_9_a5/}
}