# Exercise 6: Reuse content from another book

So far, you've been working inside your own book. But what if someone else has already written a page you’d like to reuse? Instead of copying it, you can **include it directly** into your own book using the `external:` feature in your `_toc.yml`.

You can find the link to reuse in one of two ways:

* Use the [TeachBooks Recombiner](https://teachbooks.io/recombiner/) to select and copy the link.
* If the page isn't listed in the Recombiner, find the link manually in the GitHub repository.

::::::{topic} Exercise objective
Can you include a page from someone else’s book into your own using `external:` in your `_toc.yml`?
::::::


1. Find the page you want to reuse:

   * Option 1: Open the [TeachBooks Recombiner](https://teachbooks.io/recombiner/), select the book and chapter(s) you want to reuse, and click *Show how do it yourself instructions*. Copy the `external:` link provided.
   * Option 2: If the page isn’t in the Recombiner, find it manually:

     * Go to the repository (e.g., [TeachBooks Manual on GitHub](https://github.com/TeachBooks/manual)).
     * Browse the files and find the `.md` page you want (e.g., `README.md`, `workflows/collaboration.md`).
     * Copy the raw link in this format:

       ```yaml
       - external: https://github.com/TeachBooks/manual/blob/release/book/examples/book_structure.md
       ```

2. Add the `external:` link into `chapters:` section of your `_toc.yml` file.

3. Save the changes, commit, and push them.


````{admonition} Example
`_toc.yml` snippet:

```yaml
format: jb-book
root: intro

parts:
  - caption: Contents
    chapters:
    - file: 001
    - external: https://github.com/TeachBooks/manual/blob/release/book/examples/book_structure.md
    - file: 003
```
````

4. When you are ready, commit your changes to the repository by clicking on the green `Commit changes` button.

5. Add a commit message.

6. To see your changes, go to {octicon}`play` `Actions` - The most recent workflow run `the commit message of the commit you just made` - Wait for it to finish - In the summary, click on the link of your book shown in the table `Branches deployed` and under `Primary book at root` (getting bored of waiting? There'll be exercising on doing this locally which prevents you from waiting).

7. Do you see your change? If you don't see it click `CTRL`+`F5`/`Control`+`F5`to refresh the page. Open the reused page. At the top, you should see an **attribution box**. This confirms the external content is working correctly and shows where it was sourced from. 

```{figure} https://github.com/TeachBooks/template_figures/blob/main/external_page_attribution.png?raw=true
:name: external_page_attribution
:width: 100%
:alt: Example of attribution box shown at the top of an external page

Example of attribution box at the top of an external page.
```

```{admonition} Check your understanding
:class: note

Before moving on, make sure you understand:

* What is the benefit of linking to an external page instead of copying it?
* How does using the Recombiner simplify adding external content?
* What can you do if a page isn’t in the Recombiner?
```