The compendia of Metamath proofs us here https://us.metamath.org/ https://us.metamath.org/ All of theree are formally from axioms or other formal proofs that l

The compendia of Metamath proofs us here https://us.metamath.org/ https://us.metamath.org/ All of theree are formally from axioms or other formal proofs that lead back to their axioms, without any gaps.