I think the "best" way would be specify a class or attribute.
For example for srfi-64:

(<b id="test-equal" class="index-entry">test-equal</b> [<var>test-name</var>] <var>expected</var> <var>test-expr</var>)

A tool can translate this into:

<a href="srfi-64.html#test-equal">test-equal</a> (<a href="srfi-64.html">srfi-64</a>)

The main problem of course is these have to be added manually, though
perhaps some tool can generate an initial approximation.
I'm willing to update my SRFIs, if it comes to that.
--
	--Per Bothner
xxxxxx@bothner.com   http://per.bothner.com/