Paul, R.; Falk, G. and Feldman, J. A. "The Computer Representation of Simply Described Scenes"

Faiman, M. and J. Nievergelt, eds. (1969) Faiman, M. and J. Nievergelt, eds. "Pertinent Concepts in Computer Graphics" University of Illinois Urbana, 1969  

Languages mentioned LEAP with Graphical Extensions {1969} LEAP with graphics primitives