C. Ghidini, and L. Serafini. Proceedings AIMSA'98, 8th International Conference on Artificial Intelligence, Methodology, Systems, and Applications, volume 1480 of LNAI, page 267--280. Sozopol, Bulgaria, Springer Verlag, (September 1998)
J. Cugini, S. Laskowski, and M. Sebrechts. IST/SPIE's 12th Annual International Symposium: Electronic Imaging 2000: Visual Data Exploration and Analysis (SPIE 2000), San Jose, CA, (2000)
G. Stumme, and K. Wolff. Advances in Database Technologies. Proc. Intl. Workshop on Data Warehousing and, volume 1552 of LNCS, page 117-128. Heidelberg, Springer, (1999)