1. F.J. Corbato, PL/I as a tool for systems programming. Datamation 15(5) (1969)
2. N. Nilsson, Problem-Solving Methods in Artificial Intelligence (McGraw-Hill, 1971)
3. R.B. Benerji, Theory of Problem Solving: An Approach to Artificial Intelligence (1969)
4. T.A. Wadlow, The Xerox Alto Computer. BYTE Artif. Intell. Issue 6(9), 58–68 (1981)
5. BYTE, Artif. Intell. Issue 10(4) (1985)