Searching the archive - operators? single group only?

Today is my first day of trying out DA, and although I’m impressed, I’m coming up against some unexpected behaviour in the Search pane of the Archive.

When I type in two or more search terms, the Archive search function appears to treat them as if they’re separated by an OR. Say I’ve typed in “Sumerian chronology”; the Archive returns results containing either “Sumerian” or “chronology” but not necessarily both. I’m getting a lot of irrelevant results because, although I don’t want to see results about any type of chronology other than Sumerian, I’m getting every archived item that contains “chronology,” whether or not it contains “Sumerian”. Adding quotation marks or other operators (NEAR, BEFORE) doesn’t seem to change the behaviour. I can’t see any relevant-looking controls in Preferences. Is there a way to change this behaviour in DA? I imagine I could send the Archive to DTPro and use DTPro’s search function, but is there a simpler way?

Also, although I’ve selected a single group in the lefthand column, the search appears to range over the entire Archive - which increases the number of irrelevant results, because I want to search in a single group only. Is there a way to limit the search to a single group in the Archive, without sending that group to DTPro?