Andrzej M. Borzyszkowski Stefan Sokolowski Mathematical Foundations of Computer Science 1993, 18th International Symposium, MFCS'93, Gdansk, Poland, August 30 - September 3, 1993, Proceedings MFCS Lecture Notes in Computer Science 711 Springer 1993 3-540-57182-5 db/conf/mfcs/mfcs93.html