Does 'which' refer to the noun immediately preceding it?
Solution 1:
It technically is ambiguous, even though I think most people would read it as intended, I suppose the fact is that you could have meant something different and someone could have interpreted differently, means it really is ambiguous.
Would it not remove ambiguity to simply remove ", which" and replace with "and":
"Proposition 25 suggests a better definition of m-reducibility than given in Definition 23 and is also the one typically given in texts".
That removes the ambiguity for me at least!