  In this paper, first we revisit the formal integration of Lie algebras, which
give rise to braces in some special cases. Then we establish the formal
integration theory for complete Rota-Baxter Lie algebras, that is, we show that
there is a Rota-Baxter group with the underlying group structure given by the
Baker-Campbell-Hausdorff formula, associated to any complete Rota-Baxter Lie
algebra.
