Improving Phrase Extraction via MBR Phrase Scoring and Pruning Nan Duan author Mu Li author Ming Zhou author Lei Cui author 2011-sep 19-23 text Proceedings of Machine Translation Summit XIII: Papers Xiamen, China conference publication duan-etal-2011-improving https://aclanthology.org/2011.mtsummit-papers.20/ 2011-sep 19-23