updates

book/exercises/009.md

@@ -1,2 +1,34 @@
-# Ninth exercises
-kdjb
+# 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. Referencing can be done using target headers. (<title>)=
+
+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 ebtween bracketsfor 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. Referncing
+
+There are three types of referencing
+
+If you want to refernce in line you can use:
+
+My favourte exercise was {ref}`exercise_1`.
+
+```
+My favourte exercise was {ref}`exercise_1`.
+```
+You can specify the text of the target:
+
+{ref}`MyST syntax lecture <exercise_1>`
+
+Another alternative is to use Markdown syntax:
+
+[MyST syntax lecture](exercise_1)