Joint Optimization for Machine Translation System Combination Xiaodong He author Kristina Toutanova author 2009-08 text Proceedings of the 2009 Conference on Empirical Methods in Natural Language Processing Philipp Koehn editor Rada Mihalcea editor Association for Computational Linguistics Singapore conference publication he-toutanova-2009-joint https://aclanthology.org/D09-1125/ 2009-08 1202 1211