Fix typo in formal-spaces

formal-spaces.tex

@@ -4927,7 +4927,7 @@ \section{Algebras topologically of finite type}
 \begin{proof}
 The implications (a) $\Rightarrow$ (b), (c) $\Rightarrow$ (a),
 (d) $\Rightarrow$ (c) are straightforward from the definitions.
-Assume (b) holds and let $J \subset B$ and $I \subset A$ be as in (b).
+Assume (b) holds and let $J \subset B$ and $I \subset A$ be as in (a).
 Choose a commutative diagram
 $$
 \xymatrix{