Russell suggests to check where Wikipedia ranks in that list.
Well, the "credibility discrimination problem" is much easier on some sources (the "Rockstar ate my Hamster" headlines runners for example).
Yes, I played on the term "source", as "witness" vs "reporter", to stress in theory the human factor and in practice the paradox (inherent in the difficulties Wikipedia has to have in providing quality).
(I'd thought of noting that it's not secondary either, decided to keep it simple.)
What Wikipedia is generally good at is in providing a synoptic presentation of a topic and identifying sources that document the points, facts, or arguments it presents. I'll often mine it for resources when doing a shallow dive on a topic.
For deeper dives, I'll try to branch out further from both those and other points.