TY  - JOUR
AU  - N. G. Bulgakov
TI  - On the existence of periodic solutions to nonlinear systems
JO  - Differencialʹnye uravneniâ
PY  - 1972
SP  - 1876
EP  - 1877
VL  - 8
IS  - 10
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_1972_8_10_a17/
LA  - ru
ID  - DE_1972_8_10_a17
ER  -