Lemma 13.14.4. Assumptions and notation as in Situation 13.14.1. Let $s : X \to Y$ be an element of $S$.

1. $RF$ is defined at $X$ if and only if it is defined at $Y$. In this case the map $RF(s) : RF(X) \to RF(Y)$ between values is an isomorphism.

2. $LF$ is defined at $X$ if and only if it is defined at $Y$. In this case the map $LF(s) : LF(X) \to LF(Y)$ between values is an isomorphism.

Proof. Omitted. $\square$

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