Enlisting the Ghost: Modeling Empty Categories for Machine Translation Bing Xiang author Xiaoqiang Luo author Bowen Zhou author 2013-08 text Proceedings of the 51st Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers) Hinrich Schuetze editor Pascale Fung editor Massimo Poesio editor Association for Computational Linguistics Sofia, Bulgaria conference publication xiang-etal-2013-enlisting https://aclanthology.org/P13-1081/ 2013-08 822 831