Y. Qin, D. Song, H. Chen, W. Cheng, G. Jiang, and G. Cottrell. Proceedings of the Twenty-Sixth International Joint Conference on Artificial Intelligence, International Joint Conferences on Artificial Intelligence Organization, (August 2017)
J. Tan, X. Wan, and J. Xiao. Proceedings of the 55th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), 1, page 1171--1181. (2017)