An Empirical Study of Diversity of Word Alignment and its Symmetrization Techniques for System Combination Thoudam Doren Singh author 2015-12 text Proceedings of the 12th International Conference on Natural Language Processing Dipti Misra Sharma editor Rajeev Sangal editor Elizabeth Sherly editor NLP Association of India Trivandrum, India conference publication singh-2015-empirical https://aclanthology.org/W15-5919/ 2015-12 124 129