Corollary 2
Tag 0ACN, permanent. Cite it as [Bourbaki, Tag 0ACN].
Lie Groups and Lie Algebras, chapter III, § 4. Passage from Lie algebras to Lie groups
Let be a Lie group germ. If is commutative, is locally isomorphic to the additive Lie group .
The Lie algebra of the additive group is isomorphic to . Hence it suffices to apply Corollary 1.
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.