Sorry for the wait...
There is no current method by which you can search te text for topics
or keywords - but there *might* be n future.
We don't have "official" topics or keywords directly attached to the
text. That might change, but it certainly won't be soon.
We have experimented with "automated keywords", using automated term
extraction, with mixed results. We might have another go at this.
Any suggestions you might have would be welcome!