Matthias Höpner, Manfred Opp. About Three Equations Classes of Languages Built Up By Shuffle Operations. In Antoni W. Mazurkiewicz, editor, Mathematical Foundations of Computer Science 1976, 5th Symposium, Gdansk, Poland, September 6-10, 1976, Proceedings. Volume 45 of Lecture Notes in Computer Science, pages 337-344, Springer, 1976.
Abstract is missing.