diff --git a/src/SUMMARY.md b/src/SUMMARY.md
index 086b717d..2d2877c8 100644
--- a/src/SUMMARY.md
+++ b/src/SUMMARY.md
@@ -261,14 +261,14 @@
 - [Channels](concurrency/channels.md)
   - [Unbounded Channels](concurrency/channels/unbounded.md)
   - [Bounded Channels](concurrency/channels/bounded.md)
-- [Shared State](concurrency/shared_state.md)
-  - [Arc](concurrency/shared_state/arc.md)
-  - [Mutex](concurrency/shared_state/mutex.md)
-  - [Example](concurrency/shared_state/example.md)
 - [Send and Sync](concurrency/send-sync.md)
   - [Send](concurrency/send-sync/send.md)
   - [Sync](concurrency/send-sync/sync.md)
   - [Examples](concurrency/send-sync/examples.md)
+- [Shared State](concurrency/shared_state.md)
+  - [Arc](concurrency/shared_state/arc.md)
+  - [Mutex](concurrency/shared_state/mutex.md)
+  - [Example](concurrency/shared_state/example.md)
 - [Exercises](exercises/concurrency/morning.md)
   - [Dining Philosophers](exercises/concurrency/dining-philosophers.md)
   - [Multi-threaded Link Checker](exercises/concurrency/link-checker.md)
diff --git a/src/concurrency/send-sync/send.md b/src/concurrency/send-sync/send.md
index 8aa1be26..934ab3c5 100644
--- a/src/concurrency/send-sync/send.md
+++ b/src/concurrency/send-sync/send.md
@@ -7,3 +7,10 @@ in that thread. So the question is when you can allocate a value in one thread
 and deallocate it in another.
 
 [1]: https://doc.rust-lang.org/std/marker/trait.Send.html
+
+<details>
+
+As an example, a connection to the SQLite library must only be accessed from a
+single thread.
+
+</details>