Acquiring Topic Features to improve Event Extraction: in Pre-selected and Balanced Collections Shasha Liao author Ralph Grishman author 2011-09 text Proceedings of the International Conference Recent Advances in Natural Language Processing 2011 Ruslan Mitkov editor Galia Angelova editor Association for Computational Linguistics Hissar, Bulgaria conference publication liao-grishman-2011-acquiring https://aclanthology.org/R11-1002/ 2011-09 9 16