Eine Beschreibung contextfreier Sprachen durch endliche Mengensysteme. - Manfred Opp (Automata Theory and Formal Languages, 1975)

Allgemeine Sigma-Grammatiken. - Manfred Opp (GI Jahrestagung, 1975)

About Three Equations Classes of Languages Built Up By Shuffle Operations. - Matthias Höpner; Manfred Opp (MFCS, 1976)

Renaming and Erasing in Szilard Languages. - Matthias Höpner; Manfred Opp (ICALP, 1977)

A Normal Form Theorem for Label Grammars. - Matthias Jantzen; Manfred Opp (Math. Syst. Theory, 1981)