TY  - JOUR
AU  - S. G. Krein
AU  - V. I. Fomin
TI  - Small perturbations of singular differential equations with
JO  - Doklady Akademii Nauk
PY  - 1990
SP  - 77
EP  - 79
VL  - 314
IS  - 1
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DAN_1990_314_1_a18/
LA  - ru
ID  - DAN_1990_314_1_a18
ER  -