App/ref
From mx Help Wiki
Merging duplicate references
We have added the ability to merge duplicate references. Click 'show', then 'replace with another reference'. All tags, OTUs, etc. that were linked to the duplicate reference will be linked to the replacement.
Sharing References
All references entered into mx are available to any project; you just have to add them to your list (click 'add refs from another project').
What happens when someone in another project edits one of my references?
You will get an email notification.