Sentence examples for this is demonstrably from inspiring English sources

This is demonstrably untrue.

Again this is demonstrably false.

This is demonstrably not the case.

This is demonstrably different to other public-service professionals.

And this is demonstrably the case not just in Syria but in Iraq.

"It is essential that doctors perform male circumcision only where this is demonstrably in the best interests of the child".

Yet this was demonstrably untrue: Dora had possessed a great affection for the diary, and in old age had read regularly from it at bedtime.

Karl says that the White House has to deal with the fallout of these talking points and the revisions, but the important thing is that the talking points "began by saying that the attacks were related to the protests in Cairo" and that this was "demonstrably false".

While intuitively appealing, this idea is demonstrably false.

Now, every piece of this story is demonstrably, ludicrously wrong.

This claim is demonstrably false, as described here and here.