I view this as within the realm of "historical methods," so, happy to answer. Do you have access to LexisNexis? Google results tend to get "polluted" by more recent events, but Lexis has a reliable "sort by date" method and an appropriately limited pool of sources.

If you do have access, you'll want to find the right news database, and then make careful use of terms & connectors. "ISIS" will not work; it'll be under-inclusive. Same story with "ISIL." Look to search with something like:

(Islam! w/2 State) or ("isil" or "isis")

Those are the WestLaw connectors; I can't remember the right ones for Lexis. But that's the basic theory. Try it out!

This submission has been removed because it involves current events. To keep from discussion of politics, we have a 20-year rule here. You may want to try /r/ask_politics or another current-events focused sub.