diff --git a/content/moretypes.article b/content/moretypes.article
index 2c4a4dd..8a203aa 100644
--- a/content/moretypes.article
+++ b/content/moretypes.article
@@ -263,7 +263,9 @@
 
 Let's have some fun with functions.
 
-Implement a `fibonacci` function that returns a function (a closure) that returns successive fibonacci numbers.
+Implement a `fibonacci` function that returns a function (a closure) that
+returns successive [[https://en.wikipedia.org/wiki/Fibonacci_number][fibonacci numbers]]
+(0, 1, 1, 2, 3, 5, ...).
 
 .play moretypes/exercise-fibonacci-closure.go