**References:**

Adler, F. R.Modeling the Dynamics of Life: Calculus and Probability for Life Scientists. Brooks/Cole, Pacific Grove, CA, 1998.Glass, L. and M. C. Mackey

From Clocks to Chaos: The Rhythms of Life. Princeton University Press, Princeton, N.J., 1988.Keener, J. P. On Cardiac Arrhythmias: AV Conduction Block.

Journal of Mathematical Biology12:215-225, 1981.