As to the men, I cannot say with certainty who they may have been.

It was difficult, at any given time, to say with certainty upon which of its two stories one happened to be.

As a result, it's difficult to say with certainty how much oil is left on Earth.

I cannot say with certainty who is telling the truth.

Whether it was so in the past cannot be said with certainty.

How it came to this, no one can say with certainty.

And just about the only thing one can say with certainty is that it's not over yet.

All I can say with certainty is what comes next.

I can't say with certainty how she felt about it recently.

It is very difficult to say with certainty what they were at any particular moment.