Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DE_1997_33_5_a25, author = {Yu. V. Churin}, title = {Necessary and sufficient conditions for the existence of singular periodic solutions}, journal = {Differencialʹnye uravneni\^a}, pages = {714--715}, publisher = {mathdoc}, volume = {33}, number = {5}, year = {1997}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DE_1997_33_5_a25/} }
Yu. V. Churin. Necessary and sufficient conditions for the existence of singular periodic solutions. Differencialʹnye uravneniâ, Tome 33 (1997) no. 5, pp. 714-715. http://geodesic.mathdoc.fr/item/DE_1997_33_5_a25/