Bourbaki

Proposition 19

Tag 0546, permanent. Cite it as [Bourbaki, Tag 0546].

Commutative Algebra, chapter VII, § 4. Modules over integrally closed Noetherian domains

Let RR be a finitely generated BB-module. For RR to be reflexive, it is necessary and sufficient that R[A]R_{[A]} be a reflexive AA-module.

We have remarked in the proof of Proposition 18 that for R to be a torsion-free B-module, it is necessary and sufficient that R[A]R_{[A]} be a torsion-free A-module. We may therefore assume that R is a lattice of W=R⊗BLW = R \otimes_B L with respect to B. We shall use the following lemma:

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

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