diff --git a/book/extension_exercises/015.md b/book/extension_exercises/015.md
index 60e6278..72ae3d0 100644
--- a/book/extension_exercises/015.md
+++ b/book/extension_exercises/015.md
@@ -39,7 +39,7 @@ Branch-specific builds are useful for previewing work in progress without affect
 
 ## Customise the workflow
 
-8. The behaviour of the Deploy Book Workflow can be adapted by defining **repository variables** in your GitHub repository, as explained [here](https://docs.github.com/en/actions/learn-github-actions/variables#creating-configuration-variables-for-a-repository) or using the [VS Code Extension GitHub Actions](https://marketplace.visualstudio.com/items?itemName=GitHub.vscode-github-actions). 
+8. The behaviour of the Deploy Book Workflow can be adapted by defining **repository variables** in your GitHub repository, as explained [here](https://docs.github.com/en/actions/learn-github-actions/variables#creating-configuration-variables-for-a-repository). 
 
 
 ```{admonition} Key repository variables
@@ -69,18 +69,20 @@ Each year you release a new version of your book for students, but older cohorts
 9. Create a branch for each year (e.g. `2024`, `2025`).
 10. In repository variables, set:
 
-   * `PRIMARY_BRANCH = 2025`
-   * `BEHAVIOR_PRIMARY = redirect` (so the root redirects to the current year).
+   - `PRIMARY_BRANCH = 2025`
+   - `BEHAVIOR_PRIMARY = redirect` (so the root redirects to the current year).
 11. Push a change to the `2025` branch.
 12. Verify the URLs:
 
-   * `.../my_book/2025/` (this year)
-   * `.../my_book/2024/` (last year)
-   * `.../my_book/` (redirects to current year).
+   - `.../my_book/2025/` (this year)
+   - `.../my_book/2024/` (last year)
+   - `.../my_book/` (redirects to current year).
 
 ```{tip}
 If you want the root URL to always show a complete book instead of the in-progress year, set  
-`PRIMARY_BRANCH = 2024` and `BEHAVIOR_PRIMARY = copy`, and mark `2025` as archived.
+`PRIMARY_BRANCH = 2024` and `BEHAVIOR_PRIMARY = copy`, and mark `2025` as archived. However, we recommend
+using redirects as students might bookmark pages. If the URL changes the next academic year their bookmark
+becomes invalid or points to another page.
 ```
 
 
@@ -125,4 +127,4 @@ Before moving on, make sure you understand:
 - How can you trigger the Deploy Book Workflow?  
 - What is the purpose of `PRIMARY_BRANCH` and `BEHAVIOR_PRIMARY`?  
 - How would you set up the workflow so that both a release and a draft version of your book are available online?  
-```
\ No newline at end of file
+```