This has actually come out a bit better than I expected, because I've added a couple of features at the last minute. You can now retrieve a list of all links to a particular reference from two locations, the main "Allusions-notes" page, and the popup you see when you click on a reference link in a document. In each case, at the bottom of the reference explanation itself, you see the link "Liens à cette référence dans les documents". When you click on this link, the browser retrieves a list of links in the background and adds them into the page below the link. The links are sorted by document (so if there are two documents, there are two lists of links). When you click on an actual link, you will be taken to the location in the document where that link occurs; and the link itself will flash yellow a few times, so you can see it easily. Even if you're moving to a new page, the same reference item should open up on the page you're navigating to, so it should appear as though the reference popup stays open.

In the process, I've also done some more revisions to the layout and style, making the text a bit bigger in the popup, and moving it a little to the right; I've fixed some colour issues in the alternate stylesheets, and refactored some JavaScript code.