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∂AIL Professor Richard Tapia↓Department of Mathematical Sciences
↓Rice University↓Houston, Texas 77001∞

Dear Professor Tapia:

	While I was not Cartwright's thesis adviser, his thesis
contained the key to a problem on which I had been working for a
long time - the characterization of recursive programs in first order
logic.  His breakthrough had a number of consequences, and we wrote
several papers combining his ideas with some of mine.

	Cartwright is intelligent, energetic and personable.  He has
had several good research ideas expressed in publication
since his thesis, and therefore I think
there is unusually good evidence that he will make further substantial
contributions to the theory of computer programs.
His one major weakness is that he doesn't know as much mathematical logic
as he should for his research area.  This is partly our fault, but his
research interests changed while was finishing his thesis.

	If there were another opening here in theory, I would push his
candidacy.

.sgn