Lemma 38.7.6. Assumption and notation as in Lemma 38.7.1. Assume moreover that N is projective as an R-module. Then each s \in \Sigma defines a universally injective R-module map s : N \to N, and the map N \to \Sigma ^{-1}N is R-universally injective.
Proof. Pick s \in \Sigma . By Lemma 38.7.5 the map s : N \to N is universally injective. The map N \to \Sigma ^{-1}N is universally injective as the directed colimit of the maps s : N \to N. \square
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