(en)Heinz von Foerster, Margaret Mead e Hans Lukas Teuber: Cybernetics, Circular Causal and Feedback Mechanisms in Biological and Social Systems S/t Transactions of the Seventh Conference, March 23-24, 1950, Nòva York, ed: Josiah Macy, Jr. Foundation in actes de la 7a « conferéncia Macy » 1951 251p.