Meduna, A., & Kopeček, T. (2004). Simple-Semi-Conditional Versions of Matrix Grammars with a Reduced Regulating Mechanism. Computing and Informatics, 23(3), 287–302. https://cai.type.sk/content/2004/3/simple-semi-conditional-versions-of-matrix-grammars-with-a-reduced-regulating-mechanism/