diff --git a/book/syntax_exercises/013.md b/book/syntax_exercises/013.md
index 3cadb1a..62db026 100644
--- a/book/syntax_exercises/013.md
+++ b/book/syntax_exercises/013.md
@@ -117,6 +117,8 @@ Heres's how each style will appear for the example in the shared bibliography:
 - `super` → ¹
 - `number` → [1]
 
+Feeling brave? You can also use APA references, although this is not a default option. More information on to set this up is available in the [TeachBooks manual](https://teachbooks.io/manual/features/apa.html)
+
 ```
 
 8. You can also change the **bibliography style** (how the reference list is formatted) using the `:style:` option in the `{bibliography}` directive. Try replacing the style with the following, and see how the bibliography style changes.