diff --git a/toc.org b/toc.org
index fb9fdab..9b95791 100644
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@@ -32,3 +32,4 @@
 - [[./_subsections/lesson-01.org][Lesson 01 | Course Overview + The Shell]]
 - [[./_subsections/lesson-02.org][Lesson 02 | Shell Tools and Scripting]]
 - [[./_subsections/lesson-03.org][Lesson 03 | Editors (vim)]]
+- [[./_subsections/lesson-04.org][Lesson 04 | Data Wrangling]]