diff --git a/intro.Rmd b/intro.Rmd
index adf9bd4..659be75 100644
--- a/intro.Rmd
+++ b/intro.Rmd
@@ -145,3 +145,8 @@ You will not be able to use the functions, objects, and help files in a package
 * StackOverflow ([reprex](https://github.com/jennybc/reprex))
 
 * Twitter
+
+## Acknowledgements
+
+* Jenny Bryan and Lionel Henry for many helpful discussions around working
+  with lists and list-columns.