1. An algorithm for the organization of information;Adel'son-Vel'skii;Soviet Math. Dokl.,1962
2. Expert systems for configuration at Digital: XCON and beyond;Barker;Communications of the ACM,1989
3. The R∗-tree: An efficient and robust access method for points and rectangles;Beckmann,1990
4. Index support for rule activation;Brant,1993