Lecture Notes in Computer Science Edited by G. Goos, J. Hartmanis and J. van Leeuwen 1563 3 Berlin Heidelberg New York Barcelona Hong Kong London Milan Paris Singapore Tokyo Christoph Meinel Sophie Tison (Eds.) STACS 99 16th Annual Symposium on Theoretical Aspects of Computer Science Trier, Germany, March 4-6, 1999 Proceedings 13 Series Editors Gerhard Goos, Karlsruhe University, Germany Juris Hartmanis, Cornell University, NY, USA Jan van Leeuwen, Utrecht University, The Netherlands Volume Editors Christoph Meinel FB IV – Informatik, Universit¨ at Trier D-54286 Trier, Germany E-mail:
[email protected] Sophie Tison LIFL, Universit´e de Lille I, Bˆatiment 3 F-59655 Villeneuve d’Ascq Cedex, France E-mail:
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