diff --git a/docs/09-bootstrapping-kubernetes-workers.md b/docs/09-bootstrapping-kubernetes-workers.md
index 7b9c023..9818fb6 100644
--- a/docs/09-bootstrapping-kubernetes-workers.md
+++ b/docs/09-bootstrapping-kubernetes-workers.md
@@ -102,6 +102,8 @@ worker-1$ wget -q --show-progress --https-only --timestamping \
   https://storage.googleapis.com/kubernetes-release/release/v1.13.0/bin/linux/amd64/kubelet
 ```
 
+Reference: https://kubernetes.io/docs/setup/release/#node-binaries
+
 Create the installation directories:
 
 ```