[alisonkisk]

But how do you know those are credible? It's fundamentally impossible to decide from first principles. You have to choose where to put your faith. Longstanding reputation is one popular way, but old things can sell out, or can be fairy tails (like at least all but one religions).

[deeeeplearning]

Right but at least Impact Factor gives you some kind of objective idea of the importance of a journal. Most researchers know Science and Nature are elite journals and impact factor at least backs that up by showing that their papers are highly cited by other "experts" in the field. But as I said it's still not perfect.