Remark
Tag 063C, permanent. Cite it as [Bourbaki, Tag 063C].
Algebra, chapter III, § 7. Exterior algebras
Let be the direct sum of another family of -modules with as indexing set and, for all , let be an -linear mapping, whence there is an -linear mapping (II, § 1, no. 6, Proposition 7). Then the diagram
is commutative (cf. § 4, no. 5, Corollary to Proposition 8).
The sub--module of with which is identified by means of the isomorphism can be described more precisely. For every finite subset of , we write , so that relative to the directed set of finite subsets of , by definition (, no. 8, Remark 1). For every family (therefore with finite support) such that and every finite subset of containing the support of the family , we write
so that the submodule of elements of degree in is the direct sum of the for all families of support contained in and such that
(, no. 7, Proposition 10 and no. 8). By way of convention we write for the families whose support is not contained in ; then
E_{J,n} can also be called the direct sum of all the , where runs through the set of all families such that . Since is identified with , clearly also for two finite subsets of and a family of support contained in , the canonical mapping (restriction of the canonical mapping to ) is bijective. If we write, for all ,
it is then seen that, taking account of II, § 6, no. 2, Proposition 5, we have:
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.
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