TY  - JOUR
AU  - I. I. Pleshkan
TI  - Conditions for the isochronism of systems of two differential equations
JO  - Differencialʹnye uravneniâ
PY  - 1968
SP  - 1991
EP  - 1993
VL  - 4
IS  - 11
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_1968_4_11_a6/
LA  - ru
ID  - DE_1968_4_11_a6
ER  -