Document URL: 
https://docs.openshift.com/container-platform/3.9/upgrading/automated_upgrades.html#preparing-for-an-automated-upgrade

Section Number and Name: 
Preparing for an Automated Upgrade

Describe the issue: 
"Before attempting the upgrade, follow the guidance in [Environment health checks] to verify the cluster’s health. This will confirm that nodes are in the Ready state, running the expected starting version, and will ensure that there are no diagnostic errors or warnings."

Environment health check link is incorrect

https://docs.openshift.com/container-platform/3.9/day_two_guide/environment_health_checks.html.html#day_two_environment_health_checks

correct:
https://docs.openshift.com/container-platform/3.9/day_two_guide/environment_health_checks.html#day_two_environment_health_checks

Note the additional ".html"