W. Zou, R. Socher, D. Cer, and C. Manning. Proceedings of the 2013 Conference on Empirical Methods in Natural Language Processing, page 1393--1398. (2013)
D. Tsarkov, and I. Horrocks. Proc. of the Int. Joint Conf. on Automated Reasoning (IJCAR 2006), volume 4130 of Lecture Notes in Artificial Intelligence, page 292--297. Springer, (2006)