diff --git a/part3/README.md b/part3/README.md
index f1c86ca..7c51cfc 100644
--- a/part3/README.md
+++ b/part3/README.md
@@ -15,3 +15,8 @@ to fail; in that case, just run `elm package install` again.)
 ```bash
 elm live Main.elm --open -- --output=elm.js
 ```
+
+## References
+
+* [`onClick` documentation](http://package.elm-lang.org/packages/evancz/elm-html/4.0.2/Html-Events#onClick)
+* [record update syntax reference](http://elm-lang.org/docs/syntax#records) (e.g. `{ model | query = "foo" }`)
diff --git a/part4/README.md b/part4/README.md
index b8a4094..3799a0b 100644
--- a/part4/README.md
+++ b/part4/README.md
@@ -15,3 +15,7 @@ to fail; in that case, just run `elm package install` again.)
 ```bash
 elm live Main.elm --open -- --output=elm.js
 ```
+
+## References
+
+* [Union Types syntax reference](http://elm-lang.org/docs/syntax#union-types)