%0 Journal Article %A Matas, VladimĂ­r %T On non-existence of periodic solutions of an important differential equation %J Applications of Mathematics %D 1973 %P 213-226 %V 18 %N 4 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.21136/AM.1973.103474/ %R 10.21136/AM.1973.103474 %G en %F 10_21136_AM_1973_103474