Comment 12 for bug 1642023

I added the information on the content Reference in the following Pull Request
https://github.com/evergreen-library-system/Evergreen/pull/85

If you are looking for examples I have made a git repository here to examples
I'm going to look at adding examples to this repository, and the find a way to migrate this in to the actual docs.
https://github.com/alynn26/Evergreen-Receipts