Fix copy-paste typo

Author: while0pass

index.md

@@ -121,7 +121,7 @@ The exercises of this section focus on creating a Python function according to a
 
 [**IDEA instructions: merge sort**](material/merge-sort.pdf): A nonverbal definition of the merge sort algorithm, created by Sándor P. Fekete and Sebastian Morr. It is also available in the [IDEA website](https://idea-instructions.com/merge-sort/).
 
-[**IDEA instructions: quick sort**](material/merge-sort.pdf): A nonverbal definition of the quick sort algorithm, created by Sándor P. Fekete and Sebastian Morr. It is also available in the [IDEA website](https://idea-instructions.com/quick-sort/).
+[**IDEA instructions: quick sort**](material/quick-sort.pdf): A nonverbal definition of the quick sort algorithm, created by Sándor P. Fekete and Sebastian Morr. It is also available in the [IDEA website](https://idea-instructions.com/quick-sort/).
 
 [**Computer Science - Khan Academy**](https://www.khanacademy.org/computing/computer-science): a collection of videos and material introducing several Computer Science concepts, including an entire section on [algorithms](https://www.khanacademy.org/computing/computer-science/algorithms).
 
@@ -138,4 +138,4 @@ All the software has been released with an [ISC License](https://opensource.org/
 
 All the data are released under a [CC0 1.0 Universal (CC0 1.0) - Public Domain Dedication](https://creativecommons.org/publicdomain/zero/1.0/legalcode).
 
-The licenses mentioned above apply to all the entities unless otherwise specified. More information about the licenses are available on the [GitHub repository](https://github.com/comp-think/comp-think.github.io/blob/master/LICENSE.md) of the book.
+The licenses mentioned above apply to all the entities unless otherwise specified. More information about the licenses are available on the [GitHub repository](https://github.com/comp-think/comp-think.github.io/blob/master/LICENSE.md) of the book.