%0 Journal Article %A Schulze-Halberg, Axel %T A simple method for constructing non-liouvillian first integrals of autonomous planar systems %J Czechoslovak Mathematical Journal %D 2006 %P 987-999 %V 56 %N 3 %I mathdoc %U https://geodesic-test.mathdoc.fr/item/CMJ_2006__56_3_a17/ %G en %F CMJ_2006__56_3_a17