1. Batten, L., National capital urban planning project: development of a 3-D GIS, inProceedings of GIS/LIS'89 ACSM/ASPRS, Falls Church, VA, 1989, 781-786.
2. Buchele, S. and Crawford, R. Three-Dimensional Halfspace Constructive Solid Geometry Tree Construction from Implicit Boundary Representations, SM'03, Seattle, WA, June 2003.