diff --git a/1.9/ja/book/lang-items.md b/1.9/ja/book/lang-items.md
index 48879000..48b34ba6 100644
--- a/1.9/ja/book/lang-items.md
+++ b/1.9/ja/book/lang-items.md
@@ -46,11 +46,17 @@ unsafe fn allocate(size: usize, _align: usize) -> *mut u8 {
 
     p
 }
+
 #[lang = "exchange_free"]
 unsafe fn deallocate(ptr: *mut u8, _size: usize, _align: usize) {
     libc::free(ptr as *mut libc::c_void)
 }
 
+#[lang = "box_free"]
+unsafe fn box_free<T>(ptr: *mut T) {
+    deallocate(ptr as *mut u8, ::core::mem::size_of::<T>(), ::core::mem::align_of::<T>());
+}
+
 #[start]
 fn main(argc: isize, argv: *const *const u8) -> isize {
     let x = box 1;
diff --git a/diff-1.6.0..1.9.0/src/doc/book/lang-items.md b/diff-1.6.0..1.9.0/src/doc/book/lang-items.md
deleted file mode 100644
index 9044ac39..00000000
--- a/diff-1.6.0..1.9.0/src/doc/book/lang-items.md
+++ /dev/null
@@ -1,21 +0,0 @@
---- a/src/doc/book/lang-items.md
-+++ b/src/doc/book/lang-items.md
-@@ -39,11 +39,17 @@ unsafe fn allocate(size: usize, _align: usize) -> *mut u8 {
- 
-     p
- }
-+
- #[lang = "exchange_free"]
- unsafe fn deallocate(ptr: *mut u8, _size: usize, _align: usize) {
-     libc::free(ptr as *mut libc::c_void)
- }
- 
-+#[lang = "box_free"]
-+unsafe fn box_free<T>(ptr: *mut T) {
-+    deallocate(ptr as *mut u8, ::core::mem::size_of::<T>(), ::core::mem::align_of::<T>());
-+}
-+
- #[start]
- fn main(argc: isize, argv: *const *const u8) -> isize {
-     let x = box 1;
-diff --git a/src/doc/book/learn-rust.md b/src/doc/book/learn-rust.md