diff --git a/book/_toc.yml b/book/_toc.yml
index 91a0b9f..ad5003f 100644
--- a/book/_toc.yml
+++ b/book/_toc.yml
@@ -20,7 +20,6 @@ parts:
       sections:
       - file: syntax_exercises/007.md
       - file: syntax_exercises/008.md
-      - file: syntax_exercises/009.md
     - file: references.md
     - file: changelog.md
     - file: credits.md
diff --git a/book/syntax_exercises/009.md b/book/syntax_exercises/009.md
deleted file mode 100644
index c228e49..0000000
--- a/book/syntax_exercises/009.md
+++ /dev/null
@@ -1,45 +0,0 @@
-# Exercise 9: Referencing using target headers
-
-It can be really useful to refer to a specific section in your book  while working in a different file.
-
-::::::{topic} Exercise objective
-Can you add cross-references to headers?
-::::::
-
-1. Navigate to the file you want to work in (for example `book/some_content/overview.md`) and make sure you're in the correct branch.
-
-2. Identify the section you want to reference and name it between brackets for example `exercise_1`.
-
-```
-(exercise_1)=
-# Exercise 1: First file edit
-
-Let's start with the most basic edit: add some text to a file and see that the website is updated...
-
-```
-
-3. There are three types of referencing:
-
-* You can use the standard title text which will be the title after the target header
-
-My favourite exercise was {ref}`exercise_1`.
-
-```
-My favourite exercise was {ref}`exercise_1`.
-```
-* You can also specify the title text of the target header (aka specify what the link will say):
-
-My favourite exercise was {ref}`the first one <exercise_1>`.
-
-```
-My favourite exercise was {ref}`the first one <exercise_1>`.
-```
-
-* You can also use Markdown syntax, then the title text is also fully customizable.
-
-My favourite exercise was [this one](exercise_1).
-
-```
-My favourite exercise was [this one](exercise_1).
-```
-