1. Zipf, G. K. Human Behavior and the Principle of Least Effort (Addison-Wesley, Cambridge, Massachusetts, 1949).
2. Mantegna, R. N. et al. Phys. Rev. E 52, 2939–2950 (1995).
3. Gunther, R. et al. Int. J. Theor. Phys. 35, 395–417 (1996).
4. http://www.parc.xerox.com/iea/www/growth.html
5. Crow, E. L & Shimizu, K. Lognormal Distributions: Theory and Applications (Dekker, New York, 1988).