TY  - JOUR
AU  - H. Gacki
AU  - I. Janus
TI  - On periodic solutions of second order nonlinear differentia equations with singularities
JO  - Commentationes Mathematicae
PY  - 1991
SP  -  293
EP  - 299
VL  - 30
IS  - 2
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/articles/10.14708/cm.v30i2.6316/
DO  - 10.14708/cm.v30i2.6316
LA  - pl
ID  - 10_14708_cm_v30i2_6316
ER  -