@article{DE_1991_27_6_a24,
     author = {E. G. Zelkin},
     title = {Transformation of partial differential equations with nonseparable variables into a system of two ordinary differential equations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1081--1084},
     publisher = {mathdoc},
     volume = {27},
     number = {6},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1991_27_6_a24/}
}