diff --git a/extras/free-books.md b/extras/free-books.md
index 09ff63b..af27cb0 100644
--- a/extras/free-books.md
+++ b/extras/free-books.md
@@ -79,6 +79,7 @@ Name | Author(s)
 ### Computer Architecture
 
 ### Operating Systems
+Name | Author(s)
 :-- | :--: 
 [Operating Systems: Three Easy Pieces](http://pages.cs.wisc.edu/~remzi/OSTEP/) |Remzi H. Arpaci-Dusseau, Andrea C. Arpaci-Dusseau