Cowen, R. 1994. History of Life. 2nd ed. Cambridge, MA: Blackwell Scientific Publications.

Dalrymple. G. B. 1991. The Age of the Earth. Palo Alto, CA: Stanford University Press.

Faure, G. 1986. Principles of Isotope Geology. 2nd ed. New York: John Wiley and Sons.

Geyh, M. A., and H. Schleicher. 1990. Absolute Age Determination. New York: Springer-Verlag.

Gould, S. J. 1988. Time's Arrow/Time's Cycle. Boston: Harvard University Press.

Raup, D. M. 1991. Extinction: Bad Genes or Bad Luck? New York: W. W. Norton and Company.