TY  - JOUR
AU  - M. C. Konstantinov
TI  - Some sufficient conditions for the existence of periodic solutions of nonlinear systems of two differential equations
JO  - Differencialʹnye uravneniâ
PY  - 1984
SP  - 1632
EP  - 1634
VL  - 20
IS  - 9
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_1984_20_9_a24/
LA  - ru
ID  - DE_1984_20_9_a24
ER  -