Voir la notice de l'article provenant de la source Math-Net.Ru
@article{DAN_1990_314_1_a18, author = {S. G. Krein and V. I. Fomin}, title = {Small perturbations of singular differential equations with}, journal = {Doklady Akademii Nauk}, pages = {77--79}, publisher = {mathdoc}, volume = {314}, number = {1}, year = {1990}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1990_314_1_a18/} }
S. G. Krein; V. I. Fomin. Small perturbations of singular differential equations with. Doklady Akademii Nauk, Tome 314 (1990) no. 1, pp. 77-79. http://geodesic.mathdoc.fr/item/DAN_1990_314_1_a18/