Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DE_1968_4_3_a19, author = {V. B. Ryvkin}, title = {Letter to the editor}, journal = {Differencialʹnye uravneni\^a}, pages = {556}, publisher = {mathdoc}, volume = {4}, number = {3}, year = {1968}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1968_4_3_a19/} }
V. B. Ryvkin. Letter to the editor. Differencialʹnye uravneniâ, Tome 4 (1968) no. 3. http://geodesic.mathdoc.fr/item/DE_1968_4_3_a19/