, James L. &amp; Rumelhart, David E.,
|'Explorations in Parallel Distributed Processing:
| A Handbook of Models, Programs, and Exercises',
| MIT Press, Cambridge, MA, 1988.

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HP: The simplest case of symbol manipulation in my view is the gene.  DNA is copied
    sequentially one-base-at-a-time and translated one-codon-at-a-time.  This is called
    copying, reading, and translating just because it has the form of a language.  