Introduction to Vertex Operator Algebras

--- Base version+++ Proposed version@@ -109,7 +109,7 @@  **Exercise.** Check that normality makes the quotient action well-defined and that being fixed by $G/H$ inside $V^H$ is equivalent to being fixed by $G$. The quotient action need not be faithful for a general $V$; the displayed equality uses its fixed vectors. -The construction above requires no rationality assumption. Questions about modules, rationality, and extensions involving twisted sectors will be treated after module theory is introduced.+  ## References