1. 1. ISO International Standard Organization; Information Processing Systems - Computer Graphics; ISO/JTC1/SC24/WG1 RM201989 : Computer Graphics Reference Model.
2. 2. ISO International Standard Organization ; Information Processing Systems - Computer Graphics; GKS-3D ISO/IEC IS 88051988 : Graphical Kernel System for Three Dimensions.
3. 3. ISO International Standard Organization ; Information Processing Systems - Computer Graphics; PHIGS ISO/IEC/JTC1/SC24 DIS95921987 : Programmer's Hierarchical Interactive Graphics System.
4. 4. ISO International Standard Organization ; Information Processing Systems - Computer Graphics; GKS ISO IS 7942, DIN 66252, 1985 : Graphical Kernel System.
5. Guidelines for determining when to use GKS and when to use PHIGS