%0 Journal Article
%A H. Gacki
%A I. Janus
%T On periodic solutions of second order nonlinear differentia equations with singularities
%J Commentationes Mathematicae
%D 1991
%P  293-299
%V 30
%N 2
%I mathdoc
%U http://geodesic.mathdoc.fr/articles/10.14708/cm.v30i2.6316/
%R 10.14708/cm.v30i2.6316
%G pl
%F 10_14708_cm_v30i2_6316