1. N. Wiener, Cybernetics (Wiley, New York, and Hermann, Paris, 1948)
2. J. J. Hopfield, Proc. Natl. Acad. Sci. USA 79, 2554–2558 (1982)
3. T. E. Posch, USCEE report 290 (1968)
4. M. Minsky and S. Papert,Perceptrons: An Introduction to Computational Geometry (MIT Press, Cambridge, Mass., 1969) An expanded 2nd edition appeared in 1988. This book is a gold mine of insight.
5. J. J. Hopfield, Proc. Natl. Acad. Sci. USA 81, 3088–3092 (1984)