adding link to service principal doc from kubernetes trouble shooting section
@@ -202,6 +202,8 @@ read and **write** permissions to the target Subscription.
`Nov 10 16:35:22 k8s-master-43D6F832-0 docker[3177]: E1110 16:35:22.840688 3201 kubelet_node_status.go:69] Unable to construct api.Node object for kubelet: failed to get external ID from cloud provider: autorest#WithErrorUnlessStatusCode: POST https://login.microsoftonline.com/72f988bf-86f1-41af-91ab-2d7cd011db47/oauth2/token?api-version=1.0 failed with 400 Bad Request: StatusCode=400`
+3. [Link](serviceprincipal.md) to documentation on how to create/configure a service principal for an ACS-Engine Kubernetes cluster.
+
## Learning More
Here are recommended links to learn more about Kubernetes:
