The ref argument of \x marks the link as reference, e.g.:
Trump said this and that.\x[donald-trump-access-hollywood-tape]{ref}

= Donald Trump Access Hollywood tape
renders something like:
Trump said this and that.<a href="donald-trump-access-hollywood-tape">*</a>
This could currently be replicated without ref by just using:
Trump said this and that.\x[donald-trump-access-hollywood-tape][*]
but later on we might add more precise reference fields like the page of a book or date fetched as Wikipedia supports.