@article{Meduna_Gopalaratnam_1994, title={On semi-conditional grammars with productions having either forbidding or permitting conditions}, volume={11}, url={https://cyber.bibl.u-szeged.hu/index.php/actcybern/article/view/3435}, number={4}, journal={Acta Cybernetica}, author={Meduna, Alexander and Gopalaratnam, A.}, year={1994}, month={Jan.}, pages={307-323} }