diff --git a/book/contents/advance/lifetime/static.md b/book/contents/advance/lifetime/static.md
index 7b20f80b..2b45c47e 100644
--- a/book/contents/advance/lifetime/static.md
+++ b/book/contents/advance/lifetime/static.md
@@ -38,7 +38,7 @@ fn print<T: Display + 'static>(message: &T) {
 
 但是，**`&'static` 生命周期针对的仅仅是引用，而不是持有该引用的变量，对于变量来说，还是要遵循相应的作用域规则** :
 ```rust
-se std::{slice::from_raw_parts, str::from_utf8_unchecked};
+use std::{slice::from_raw_parts, str::from_utf8_unchecked};
 
 fn get_memory_location() -> (usize, usize) {
   // “Hello World” 是字符串字面量，因此它的生命周期是 `'static`.
diff --git a/book/excercises/Readme.md b/book/excercises/Readme.md
deleted file mode 100644
index 27442c86..00000000
--- a/book/excercises/Readme.md
+++ /dev/null
@@ -1 +0,0 @@
-# Rust语言圣经课后练习题
\ No newline at end of file
diff --git a/book/excercises/closure.md b/book/excercises/closure.md
deleted file mode 100644
index d2c81dc5..00000000
--- a/book/excercises/closure.md
+++ /dev/null
@@ -1,2 +0,0 @@
-# 闭包
-
diff --git a/book/excercises/lifetime.md b/book/excercises/lifetime.md
deleted file mode 100644
index 40439f4e..00000000
--- a/book/excercises/lifetime.md
+++ /dev/null
@@ -1,26 +0,0 @@
-## 生命周期消除
-
-```rust
-fn print(s: &str);                                      // elided
-fn print<'a>(s: &'a str);                               // expanded
-
-fn debug(lvl: usize, s: &str);                          // elided
-fn debug<'a>(lvl: usize, s: &'a str);                   // expanded
-
-fn substr(s: &str, until: usize) -> &str;               // elided
-fn substr<'a>(s: &'a str, until: usize) -> &'a str;     // expanded
-
-fn get_str() -> &str;                                   // ILLEGAL
-
-fn frob(s: &str, t: &str) -> &str;                      // ILLEGAL
-
-fn get_mut(&mut self) -> &mut T;                        // elided
-fn get_mut<'a>(&'a mut self) -> &'a mut T;              // expanded
-
-fn args<T: ToCStr>(&mut self, args: &[T]) -> &mut Command                  // elided
-fn args<'a, 'b, T: ToCStr>(&'a mut self, args: &'b [T]) -> &'a mut Command // expanded
-
-fn new(buf: &mut [u8]) -> BufWriter;                    // elided
-fn new(buf: &mut [u8]) -> BufWriter<'_>;                // elided (with `rust_2018_idioms`)
-fn new<'a>(buf: &'a mut [u8]) -> BufWriter<'a>          // expanded
-```
\ No newline at end of file