Creating simple back links

As site editor managing content with "see also" links, I would like the target content to link back to the content I'm updating – if it was not already linked to something else. This is important since it helps visitors find related content, and it decreases the need for manual work from my part.

Required Preparations: 

* A content type with an entity reference field to other content (see attached feature)
* Required modules: Entity reference

Additional Resources: 
Solution Video: