A very introductory paper on
cryptography [pdf]
(covers substitution ciphers, the Vigenere cipher, one-time pads, the Hill
cipher), developed as a professional development workshop given to middle
school teachers as part of the
MSTP project I was involved in.
An Introduction to Fatou and Julia Sets
appears in Fractals, Wavelets, and their Applications,
edited by C. Bandt, M. Barnsely, R. Devaney, K.J. Falconer, V Kannan, V. Kumar.
pp. 37-60.