Christoph Hormann wrote:
>Nice, but the really interesting question is how you can proove that
>these three ways are the only ones...
>
>Christoph
>

See Tor Olav's reference:

http://mathworld.wolfram.com/Torus.html

If I'm reading the proof at the bottom of the page correctly, (42)& (44)
establishes necessity as well as sufficiency.  And I agree, that is the
interesting question.

Dave Matthews

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