Fix typo

ProbAndMeasure/07_ergodic_theory.tex

@@ -33,7 +33,7 @@ \subsection{Laws of Large Numbers}
 	So we can assume $\mu = 0$.
 	For distinct indices $i, j, k, \ell$, by independence and the Cauchy--Schwarz inequality, we have
 	\begin{align*}
-        0 = \expect{X_i X_j X_k X_\ell} = \expect{X_i^2 X_j X_j} = \expect{X_i^3 X_j};\quad \expect{X_i^2 X_j^2} \leq \sqrt{\expect{X_i^4}}\sqrt{\expect{X_j^4}} \leq M
+        0 = \expect{X_i X_j X_k X_\ell} = \expect{X_i^2 X_j X_k} = \expect{X_i^3 X_j};\quad \expect{X_i^2 X_j^2} \leq \sqrt{\expect{X_i^4}}\sqrt{\expect{X_j^4}} \leq M
     \end{align*}
 	So we can compute
 	\begin{align*}