Ralf Hartmut Güting Dimitris Papadias Frederick H. Lochovsky Advances in Spatial Databases, 6th International Symposium, SSD'99, Hong Kong, China, July 20-23, 1999, Proceedings Lecture Notes in Computer Science 1651 Springer 1999 3-540-66247-2 db/conf/ssd/ssd99.html