Martin Breunig, Armin B. Cremers, Wolfgang Müller, Jörg Siebeck. New Methods for Topological Clustering and Spatial Access in Object-Oriented 3D Databases. In Walid G. Aref, editor, ACM-GIS 2001, Proceedings of the Ninth ACM International Symposium on Advances in Geographic Information Systems, Atlanta, GA, USA, November 9-10, 2001. pages 148-153, ACM, 2001.