diff --git a/src/measure/sets/elementary.tex b/src/measure/sets/elementary.tex
index 6fcb9ad..2495eb3 100644
--- a/src/measure/sets/elementary.tex
+++ b/src/measure/sets/elementary.tex
@@ -7,7 +7,7 @@
     \begin{enumerate}
         \item[(P1)] $\emptyset \in \ce$.
         \item[(P2)] For any $A, B \in \ce$, $A \cap B \in \ce$.
-        \item[(E)] For any $E, F \in \ce$ with $E \subset F$, there exists $\seqf{E_j} \subset \ce$ such that $E \setminus F = \bigsqcup_{j = 1}^n E_j$.
+        \item[(E)] For any $E, F \in \ce$ with $E \subset F$, there exists $\seqf{E_j} \subset \ce$ such that $F \setminus E = \bigsqcup_{j = 1}^n E_j$.
     \end{enumerate}
 
     If $X \in \ce$, then (E) may be replaced with