Nerve Axon Equations: III Stability of the Nerve Impulse John Evans Indiana University Mathematics Journal 1973 text pdf 10.1512/iumj.1973.22.22048 10.1512/iumj.1973.22.22048 en Indiana Univ. Math. J. 22 (1973) 577 - 593 state-of-the-art mathematics http://iumj.org/access/