PEM: A Paraphrase Evaluation Metric Exploiting Parallel Texts Chang Liu author Daniel Dahlmeier author Hwee Tou Ng author 2010-10 text Proceedings of the 2010 Conference on Empirical Methods in Natural Language Processing Hang Li editor Lluís Màrquez editor Association for Computational Linguistics Cambridge, MA conference publication liu-etal-2010-pem https://aclanthology.org/D10-1090/ 2010-10 923 932