S. Oyanagi, K. Kubota, and A. Nakase. in: WEBKDD 2001—Mining Web Log Data Across All Customers Touch Points, Third International Workshop, page 13--21. (2001)
I. Dhillon, S. Mallela, and D. Modha. Proceedings of The Ninth ACM SIGKDD International Conference on Knowledge Discovery and Data Mining(KDD-2003), page 89--98. (2003)