diff --git a/book/syntax_exercises/013.md b/book/syntax_exercises/013.md
index 5929d6c..8f03cde 100644
--- a/book/syntax_exercises/013.md
+++ b/book/syntax_exercises/013.md
@@ -2,9 +2,9 @@
 
 In this exercise, you will learn how to add a bibliography to your book and how to include references to sources using different citation styles (e.g., numeric, author–year, or label-based).
 
-\::::::{topic} Exercise objective
+::::::{topic} Exercise objective
 Can you include references in your book using a bibliography file and cite them using different formats?
-\::::::
+::::::
 
 ```{tip}
 Citing references properly gives credit to original authors and improves your writing. See the [JupyterBook guide on citations](https://jupyterbook.org/en/stable/content/citations.html) for full details.
@@ -33,7 +33,7 @@ Citing references properly gives credit to original authors and improves your wr
   year    = {1905}
 }
 ```
-4. Return to the Markdown file you are working on, and link the bibliography file using a **front matter header**. This should be placed at the very top of your file to automatically enable citations and bibliography rendering:
+4. Return to the Markdown file you are working on, and link the bibliography file using a front matter header. This should be placed at the very top of your file to automatically enable citations and bibliography rendering:
 
 ```md
 ---
@@ -63,14 +63,14 @@ You can add this `bibliography:` key in `_config.yml` to make the reference file
 
 ## Citing sources in different formats
 
-5. To cite a source in **numeric style** (default when using `unsrt`), use `[@key]`. Try the following example:
+5. To cite a source in numeric style (default when using `unsrt`), use `[@key]`. Try the following example:
 
 ```md
 Einstein's paper on relativity changed physics [@einstein1905].
 ```
 
 
-6. To cite a source in **author–year style**, change the style to `author-year` as shown below. Try this out and see how the citation from the previous step changes to the new formatting style.
+6. To cite a source in author–year style, change the style to `author-year` as shown below. Try this out and see how the citation from the previous step changes to the new formatting style.
 
 ````md
 ```{bibliography}
@@ -86,7 +86,7 @@ Einstein's paper on relativity changed physics [@einstein1905].
 @einstein1905 describes special relativity...
 ```
 
-8. You can also site **multiple references** by separating them with semicolons:
+8. You can also site multiple references by separating them with semicolons:
 
 ```md
 Several foundational works include [@einstein1905; @knuth1984].