Rastislav Kralovic Pawel Urzyczyn Mathematical Foundations of Computer Science 2006, 31st International Symposium, MFCS 2006, Stará Lesná, Slovakia, August 28-September 1, 2006, Proceedings MFCS Lecture Notes in Computer Science 4162 Springer 2006 3-540-37791-3 db/conf/mfcs/mfcs2006.html