When must Should Be Chosen Ralf Klabunde author 2005-08 text Proceedings of the Tenth European Workshop on Natural Language Generation (ENLG-05) Graham Wilcock editor Kristiina Jokinen editor Chris Mellish editor Ehud Reiter editor Association for Computational Linguistics Aberdeen, Scotland conference publication klabunde-2005-must https://aclanthology.org/W05-1622/ 2005-08