Josep Díaz Juhani Karhumäki Arto Lepistö Donald Sannella Automata, Languages and Programming: 31st International Colloquium, ICALP 2004, Turku, Finland, July 12-16, 2004. Proceedings ICALP Lecture Notes in Computer Science 3142 Springer 2004 3-540-22849-7 db/conf/icalp/icalp2004.html