* W. McCulloch, W. Pitts, "A Logical Calculus of Ideas Immanent in Nervous Activity", 1943, "Bulletin of Mathematical Biophysics" 5:115–133. Reipubblicato in "Neurocomputing: Foundations of Research". a cura di James A. Anderson and Edward Rosenfeld. MIT Press, 1988. pages 15–27 