Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DE_1980_16_10_a14, author = {V. N. Shapovalov}, title = {Separation of variables in a second-order linear differential equation}, journal = {Differencialʹnye uravneni\^a}, pages = {1864--1874}, publisher = {mathdoc}, volume = {16}, number = {10}, year = {1980}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1980_16_10_a14/} }
V. N. Shapovalov. Separation of variables in a second-order linear differential equation. Differencialʹnye uravneniâ, Tome 16 (1980) no. 10, pp. 1864-1874. http://geodesic.mathdoc.fr/item/DE_1980_16_10_a14/