[Zope] Query syntax for ZCatalog

I'm using ZCatalog to index a number of different documents. I want to write a brief help page for my website users on how to structure queries to help them find what they're looking for. Does such a document exist already? If so, could someone point me to it? If not, would I have to go into the source to figure it out, or is there an easier way? Thanks, Curtis Matthews