1. ObjEx Reference Manual,Gerrard Software Ltd, UK (1987).
2. D.A. Duce, E.V.C. Fielding and L.S. Marshall. Formal Specification of a Small Example Based on GKS, Transaction on Graphics
7 (3) pp. 180–197, 1988.
3. R.M. Gallimore, D. Coleman and V. Stavridou. UMIST OBJ: a Language for Executable Program Specification, Computer Journal
32(5) pp. 413–421, 1989.
4. ISO. Information processing systems — Computer graphics — Graphical Kernal System (GKS) functional description, ISO 7942, ISO Central Secretariat, August 1985.
5. ISO. Information processing systems — Computer graphics — Graphical Kernal System (GKS) for three dimensions (GKS-3D) functional description, ISO/IEC 8805, 1988.