1. Department of Foundations of Computer Science, University of Szeged, Árpád tér 2., H-6720 Szeged, Hungary. fulop@inf.u-szeged.hu
2. Institute for Natural Language Processing, Universität Stuttgart, Azenbergstr. 12, D-70174 Stuttgart, Germany. andreas.maletti@ims.uni-stuttgart.de
3. Faculty of Computer Science, Technische Universität Dresden, Mommsenstr. 13, D-01062 Dresden, Germany. heiko.vogler@tu-dresden.de