REFERENCES
Foster, Robert J. Historical Geology. Prentice-Hall Inc., New Jersey, 1991.
Minelli, A. Biological Systematics. Chapman & Hall Inc., London, 1993.
Panchen, Alec L. Classification Evolution and the Nature of Biology. Cambridge University Press, New York, 1992.
Patterson, T. [http://www.carleton.ca/~tpatters /teaching
/paleo/paleogate.html] last updated 1997.