1. T. A. Witten Jr. and L. M. Sander,Phys. Rev. Lett. 47:1400 (1981);Phys. Rev. B22:5686 (1983).
2. M. Eden, inProceedings of the 4th Berkeley Symposium on Mathematical Statistics and Probability, J. Neyman, ed. (University of California Press, Berkeley, 1961), VI. IV, p. 223.
3. H. Meinhardt,Models of Biological Patterns Formation (Academic Press, New-York, 1982).
4. F. Schlögl,Z. Phys. 253:147 (1972).
5. J. L. Cardy,J. Phys. A 16:L709 (1983).