New Frontiers Beyond Context-Freeness: Di-Grammars and Di-Automata. Peter Staudacher author 1993-04 text Sixth Conference of the European Chapter of the Association for Computational Linguistics Steven Krauwer editor Michael Moortgat editor Louis des Tombe editor Association for Computational Linguistics Utrecht, The Netherlands conference publication staudacher-1993-new https://aclanthology.org/E93-1042/ 1993-04