学術雑誌論文 Sophoin Khy, Yoshiharu Ishikawa, and Hiroyuki Kitagawa, "Querying Topic Evolution in Time Series Document Clusters", 日本データベース学会論文誌, Vol. 7, No. 3, pp. 7-12, 2009年1月. 国際会議論文 Yoshiharu Ishikawa, Yuichi Iijima, and Jeffrey Xu Yu, "Spatial Range Querying for Gaussian-Based Imprecise Query Objects", Proceedings of the International Conference on Data Engineering (ICDE 2009), pp. 676-687, Shangha