%0 Journal Article %A Gruska, Jozef %T A note on $\varepsilon$-rules in context-free grammars %J Kybernetika %D 1975 %P 26-31 %V 11 %N 1 %U http://geodesic.mathdoc.fr/item/KYB_1975_11_1_a2/ %G en %F KYB_1975_11_1_a2