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And my point is that if I'm reading a sentence and I don't eventually encounter a full stop then I get confused, regardless of the mathematics. If the mathematics is so complicated that it interrupts the flow of your sentence, then you shouldn't include it in the sentence.
@Sam, Sure. Actually, I think even trying to include commutative diagrams in sentences is doomed to failure. So I might have rephrased your example as: "Therefore, the following diagram commutes. <diagram> The diagram has no punctuation." Or something like that.
In the latter situation, I'd follow Kingsley Amis's maxim: "Recast your sentence!" If there's no sensible place for the correct punctuation, then you have written a bad sentence.
I seem to be getting wildly varying ratings for this answer! Perhaps I should comment that, when I wrote it, Anton had not specifically stated that he isn't interested in the proper case.
A less intelligent but more simple-minded algorithm is just to apply geometrization and deduce that the word problem is (uniformly) solvable in 3-manifold groups. If you know how to solve the word problem then it's easy to tell if a group is trivial.
The bit I like is:- "If he patches up all these points, he will have proved the Poincare Conjecture (for we shall show how Theorem 0 for n=2 implies the Poincare Conjecture) incorrectly."
Fair point. I suppose by a full answer I meant an equivalent condition to metrisability that doesn't use the notion of metrisability anywhere (eg in locally metrisable). I think that the condition provided by Jones' Theorem is necessary and sufficient (subject to some assumption about the Continuum Hypothesis).
