fix issue

Author: Sup2point0

issues/34.md

@@ -181,7 +181,7 @@ sorted(
 
 ## Further Reading
 
-- Passing callback functions into other functions is a form of [dependency injection]().
+- Passing callback functions into other functions is a form of [dependency injection<sup>↗</sup>](https://youtube.com/watch?v=J1f5b4vcxCQ).
 
 
 ---