diff --git a/Chapter-4/Chapter-4.tex b/Chapter-4/Chapter-4.tex
index 0cf5bee..038d38b 100644
--- a/Chapter-4/Chapter-4.tex
+++ b/Chapter-4/Chapter-4.tex
@@ -19,7 +19,7 @@ Let,
 %
 \begin{equation}
     \label{eq:zeldovich}
-    \braket{\phi_1}{\phi_2}
+    \braket{\phi_1 | \phi_2}
     =\lim_{\mu\to 0}\int_{0}^{\infty}e^{-\mu r^2}\phi_1(r)\phi_2(r)\,dr
 \end{equation}
 %
@@ -28,7 +28,7 @@ their asymptotic forms, $N_1 e^{ip_1r}$ and $N_2 e^{ip_2r}$ respectively. Then t
 integral can be broken into two.
 %
 \begin{spliteq}
-    \braket{\phi_1}{\phi_2} 
+    \braket{\phi_1 | \phi_2} 
     & \approx \lim_{\mu\to 0}\int_{0}^{R}e^{-\mu r^2}\phi_1(r)\phi_2(r)\,dr \\
     & \quad +N_1N_2\lim_{\mu\to 0}
     \int_{R}^{\infty}e^{-\mu r^2}e^{ip_1r}e^{ip_2r}\,dr \\
@@ -40,7 +40,7 @@ the first term, this simplifies as follows.
 %
 \begin{equation}
     \label{eq:easy}
-    \braket{\phi_1}{\phi_2} \approx \int_{0}^{R}\phi_1(r)\phi_2(r)\,dr
+    \braket{\phi_1 | \phi_2} \approx \int_{0}^{R}\phi_1(r)\phi_2(r)\,dr
     +\frac{\ii N_1 N_2 e^{\ii(p_1+p_2)R}}{p_1+p_2}
 \end{equation}
 %