Multi-document multilingual summarization and evaluation tracks in ACL 2013 MultiLing Workshop George Giannakopoulos author 2013-08 text Proceedings of the MultiLing 2013 Workshop on Multilingual Multi-document Summarization Association for Computational Linguistics Sofia, Bulgaria conference publication giannakopoulos-2013-multi https://aclanthology.org/W13-3103/ 2013-08 20 28