1. Ring dynamics and percolation in an excitable medium
2. and references therein; in Oscillations and Travelling Waves in Chemical Systems, and Eds., Wiley, New York, 1985.
3. and Self-Organization in Non-Equilibrium Systems, Wiley, New York, 1977;
4. From Being to Becoming: Time and Complexity in the Physical Sciences, Freeman, San Francisco, 1980;