Z. Zhang, S. Liu, M. Li, M. Zhou, and E. Chen. Proceedings of the 22nd Conference on Computational Natural Language Learning, CoNLL 2018, Brussels, Belgium, October 31 - November 1, 2018, page 190--199. Association for Computational Linguistics, (2018)
Y. Zhou, L. Wu, F. Weng, and H. Schmidt. Proceedings of the 2003 conference on Empirical methods in natural language processing, page 153--159. Morristown, NJ, USA, Association for Computational Linguistics, (2003)