2) B. G. Baumgart : Geometric Modelling for Computer Vision, Rep. STA-CS-74-463, Stanford Univ., Stanford, Calf., (1974).
3) I. C. Braid : Note on Geometric Modeller, Univ. of Cambridge, CAD Group Document, No. 101, (1979).
4) H. B. Voelcker et al. : An Introduction to PADL ; Characteristics, Status and Rational, Tech. Memo. 22, Production Automation Project, Univ. of Rochester, N. Y., Dec. (1974).