diff --git a/IntroductionEnvironment.md b/IntroductionEnvironment.md
index f3f2496..f735ba4 100644
--- a/IntroductionEnvironment.md
+++ b/IntroductionEnvironment.md
@@ -2,11 +2,11 @@ We create a introduction environment to display the structure of chapter. The ba
 
 ```latex
 \begin{introduction}
-	\item Definition of Theorem
-	\item Ask for help
-	\item Optimization Problem
-	\item Property of Cauchy Series
-	\item Angle of Corner
+  \item Definition of Theorem
+  \item Ask for help
+  \item Optimization Problem
+  \item Property of Cauchy Series
+  \item Angle of Corner
 \end{introduction}
 ```
 
diff --git a/章后习题.md b/章后习题.md
index 728b874..c1f2154 100644
--- a/章后习题.md
+++ b/章后习题.md
@@ -2,9 +2,9 @@
 
 ```tex
 \begin{problemset}
-	\item exercise 1
-	\item exercise 2
-	\item exercise 3
+  \item exercise 1
+  \item exercise 2
+  \item exercise 3
 \end{problemset}
 ```
 
@@ -16,7 +16,7 @@
 
 ```tex
 \begin{problemset}[Hello World]
-	\item ...
+  \item ...
 \end{problemset}
 ```
 
diff --git a/章节摘要.md b/章节摘要.md
index 996b913..f9b3395 100644
--- a/章节摘要.md
+++ b/章节摘要.md
@@ -2,11 +2,11 @@
 
 ```tex
 \begin{introduction}
-	\item Definition of Theorem
-	\item Ask for help
-	\item Optimization Problem
-	\item Property of Cauchy Series
-	\item Angle of Corner
+  \item Definition of Theorem
+  \item Ask for help
+  \item Optimization Problem
+  \item Property of Cauchy Series
+  \item Angle of Corner
 \end{introduction}
 ```