1. Erich Jantsch.Technological Planning and Social Futures. (1972). London, Associated Business Programmes Ltd. Cassell p. 16.
2. Christopher Alexander.Notes on the Synthesis of Form. (1967). Harvard University Press.
3. Herbert Simon.The Sciences of the Artificial. (1969). M.I.T. Press.
4. G. Vickers. Motivation Theory?a Cybernetic Contribution.General Systems Journal. Vol. 1. Part 1 (due 1973).