References:
Cloud, Preston. 1988. Oasis in Space. New York: W. W. Norton Company. 508 pp.

Condie, Kent C, editor. Proterozoic Crustal Evolution. 1993. Amsterdam: Elsevier Scientific Publishing Company. 537 pp.

Cowen, Richard. 2000. History of Life, third edition. London: Blackwell Science, Inc. 432 pp.

Dott, Robert H., Jr., and Donald R. Prothero. 2002. Evolution of the Earth, sixth edition. New York: McGraw-Hill, Inc. 569 pp.

Frey, Iris. 2000. The Emergence of Life on Earth: A Historical and Scientific Overview . Rutgers, New Jersey: Rutgers University Press. 327 pp.

Kutter, G. S. 1987. The Universe and Life: Origins and Evolution. Boston: Jones and Bartlett Publishers, Inc. 592 pp.

Levin, Harold L. 1996. The Earth through Time, sixth edition. Philadelphia: Saunders College Publishing. 568 pp.

Schopf, William, and Cornelius Klein, editors. 1992. The Proterozoic Biosphere: A Multidisciplinary Study. Cambridge, New York: Cambridge University Press. 1348 pp.

Schopf, J. William. 2001. Cradle of Life: The Discovery of Earth’s Earliest Fossils. Princeton, New Jersey: Princeton University Press. 336 pp.

Stanley, Steven M. Earth System History. 1999). New York: W. H. Freeman and Company. 615 pp.

Wicander, Reed, and James S. Monroe. 2000. Historical Geology: Evolution of the Earth and Life through Time, third edition. 2000. Pacific Grove, California: Brooks/Cole. 580 pp.

Links:
http://www.ucmp.berkeley.edu/precambrian/proterozoic.html - Introduction to the Proterozoic Era
http://www.palaeos.com/Proterozoic/Proterozoic.htm - Palaeos: Geological Time Scale