H. Galhardas, D. Florescu, D. Shasha, E. Simon, and C. Saita. Proceedings of the 3rd Intl. Workshop on Design and Management of Data Warehouses, DMDW'2001, Interlaken, Switzerland, June 4, 2001, volume 39 of CEUR Workshop Proceedings, page 3. CEUR-WS.org, (2001)