TY  - JOUR
AU  - G. E. Popov
TI  - On the absence of periodic solutions taking the value $x=0$ in a class of differential equations of the form $\ddot x+x=F(x,\,\dot x)$
JO  - Izvestiâ vysših učebnyh zavedenij. Matematika
PY  - 1964
SP  - 120
EP  - 122
IS  - 3
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/IVM_1964_3_a17/
LA  - ru
ID  - IVM_1964_3_a17
ER  -