1. APT Part Programming,1967
2. APT IV Computer System Manual, Volume 2, Subroutine Library A4V3,1967
3. Representations of Rigid Solid Objects;Requicha,1980
4. Computational geometry for design and manufacture;Faux,1979
5. The PADL-1.0/2 system for defining and displaying solid objects;Voelcker;ACM Comput. Graphics,1978