1. Ashby, W. R., Measuring the internal informational exchange in a system, Cybernetica, 8 (1965), 5–22.
2. Ashby, W. R., Two tables of identities governing information flows within large systems, Comm. Am. Soc. Cyb. 1, No. 2 (1969) 2–8.
3. Attneave, F., Applications of information theory to psychology, New York, 1959.
4. Blalock, H. M., Four-variable causal models and partial correlations, Am. J. Soc., 68 (1962), 182–194.
5. Broekstra, G., Constraint analysis and structure identification, Annals of Systems Research, 5 (1975), 67–80.