Webi as publication source docs

Good day,

I have a seemingly very simple question and searching for info on it is proving to be difficult.

We have a customer with literally hundreds of publications, they did not really understand how it works and what it can do, so they ended up using it in the same way one would just create a normal schedule - one publication per report per person.

They would like to know which of their webi documents are all source documents for publications.  Obviously without going to each and every publication's properties.

Is there a quick and easier way of finding this info?  Maybe via something like query builder etc?

Thanks in advance,

Haidee