1. Phillips, W. and Thorson, S. (1975) Complexity and policy planning, in Systems Thinking and the Quality of Life, Proc. Soc. for General Systems Research Annual Meeting.
2. Ashby, W.R. (1973) Some peculiarities of complex systems. Cybernetics Medicine 9: 1–8.
3. Quine, W.V.O. (1964) On simple theories of a complex world, in J. Gregg and F. Harris (Eds) Form and Strategy in Science ( Dordrecht: Reidel)
4. Wimsatt, W. (1972) Complexity and organization, in K. Schaffner and R. Cohen (Eds) Studies in the Philosophy of Sciences, Vol. XX ( Reidel, Boston)
5. Simon, EL, (1969) The architecture of complexity, in Sciences of the Artificial ( Cambridge, MA: MIT Press).