Bak, P., Tang, C., and Wiesenfeld, K., "Self-organized criticality," Phys. Rev. A 38 (1988), 364-374.

Bak, P., Chen, K., "Self-organized criticality," Sci. Am. Jan, 1991.

Bak, P., How Nature Works: The Science of Self-Organized Criticality, Springer, 1996.