Newell, A. and Simon, H. A., "GPS, A Program That Simulates Human Thought", pp279-93

Feigenbaum, E. and Feldman, J. (eds.) (1963) Feigenbaum, E. and Feldman, J. (eds.) "Computers and Thought" MIT Press, Cambridge, MA, 1963  

Languages mentioned GPS {1957} General Problem Solver IPL-V {1957} Information Processing Language v5