TY  - JOUR
AU  - N. I. Avdonin
TI  - Certain tests for the existence and absence of closed trajectories of a certain system of differential equations
JO  - Differencialʹnye uravneniâ
PY  - 1968
SP  - 639
EP  - 645
VL  - 4
IS  - 4
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_1968_4_4_a6/
LA  - ru
ID  - DE_1968_4_4_a6
ER  -