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