Adding id attributes to the reference elements themselves was enough to make the popup function, in that the reference element is copied to the popup and displayed; so that's one issue fixed. However, because the default display in the reference list shows each reference collapsed, it's also collapsed when it's copied to the popup. I need to elaborate the showReference() function a little so that it can auto-expand that stuff if necessary (without breaking the way the same function works in the context of anthology documents and articles).