TY  - JOUR
AU  - V. V. Amel'kin
AU  - I. V. Gaishun
TI  - The periodic solutions of second order systems
JO  - Differencialʹnye uravneniâ
PY  - 1974
SP  - 1560
EP  - 1564
VL  - 10
IS  - 9
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_1974_10_9_a1/
LA  - ru
ID  - DE_1974_10_9_a1
ER  -