Jarek Rossignac, Herbert B. Voelcker: Active zones in CSG for accelerating boundary evaluation, redundancy elimination, interference detection, and shading algorithms. 51-87
Volume 8, Number 2, April 1989
Gerald E. Farin: Curvature continuity and offsets for piecewise conics. 89-99
Barry Joe: Multiple-knot and rational cubic beta-splines. 100-120