adeveri

to confirm

to bear out

to ascertain the truth of

to corroborate

to give countenance to

to prove

to declare on oath

to seal

to (at)test

to testify

to verify

to vouch

to warrant

to witness

to acknowledge

to prove

to put to the proof

to test

to demonstrate

to put beyond doubt

to substantiate

to prove (to be) true

to hold true/good

to turn out to be true

to come true