Awesome Content Management Systems (in no particular order)
And their documentation
Optimizely
https://world.optimizely.com/documentation/developer-guides/CMS/
Umbraco
https://our.umbraco.com/documentation/
awesome cms's
And their documentation
https://world.optimizely.com/documentation/developer-guides/CMS/
https://our.umbraco.com/documentation/