Voelcker, H. et al "The PADL-1.0/2 system for defining and displaying solid objects" pp257-263

[Proceedings] (1980) Computer Graphics Volume 14, Number 3, July, 1980 (Proceedings of the 7th International Conference on Computer Graphics and Interactive Techniques Seattle, Washington, United States SIGRAPH 80)  

Languages mentioned PADL-1 {1978}