If you look at file manager, files will have "shortcut" or "has references" icons. For example if file in resource1 is a reference to file in resource2, when you edit resource2 you will see a "has references" icon on this file (looks like a like or sideways 8). When you edit resource1 you will see a "shortcut" icon on this file (looks like a bent arrow).

However if you browse server files only "shortcut" is displayed but the "has references" icon is not.

I found that JS exists but we never calculate or pass the data for it.