%0 Journal Article %A Tadeusz Rumak %T On the ยต-observability of some non-linear difference equations %J Annales Polonici Mathematici %D 1972 %P 315-324 %V 26 %N 3 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.4064/ap-26-3-315-324/ %R 10.4064/ap-26-3-315-324 %G en %F 10_4064_ap_26_3_315_324