1. Ackoff, R. L., and Emery, F. E. (1972).On Purposeful Systems, Aldine, Chicago.
2. Ashby, W. R. (1952).Design for a Brain, Chapman and Hall, London.
3. Bailey, K. D. (1985). Systems as clusters.Behav. Sci. 30, 98?107.
4. Bridgman, P. W. (1927).The Logic of Modem Physics, Macmillan, New York.
5. Deutsch, M. (1954). Field theory in social psychology.Handbook Soc. Psychol. 1, 181?222.