L. Lee. Proceedings of the 37th annual meeting of the Association for Computational Linguistics on Computational Linguistics, page 25--32. Morristown, NJ, USA, Association for Computational Linguistics, (1999)
P. Ziegler, C. Kiefer, C. Sturm, K. Dittrich, and A. Bernstein. 10th International Conference on Extending Database Technology (EDBT 2006), volume 3896 of Lecture Notes in Computer Science, page 59-76. Munich, Germany, March 26-31, Springer, (2006)