Give a non-legal example.3.

(Unit 2.3 built the checklist; this section systematises it as a method.)The source-hierarchy habit (rank before you rely):1. Primary > secondary — the statute itself beats the commentary; the judgment beats the case summary; the regulation beats the news report about it.2. Official > unofficial — official gazette texts, court records, certified copies against blogs and photocopies.3. Current > superseded — is this the law now? (Amended? Overruled? Repealed?)4. Peer-reviewed / editorially vetted > self-published.The skillful judgement (a four-step protocol):1. Identify the source type (primary/secondary; expert/lay; interested/independent);2. Apply the credibility criteria (vested interest, bias, track record, competence, corroboration, internal consistency — Unit 2.3's list);3. Cross-check the load-bearing facts — any fact your argument needs gets a second source;4. Grade and state your confidence — "confirmed" "probable" "single-source" "contested" — the honest grades lawyers use in advice letters.Special cases for lawyers: anonymous sources (treat as leads, not proof); translated documents (meaning drift — get a certified translation); AI-generated research (verify every citation at the primary source — the emerging professional duty); and social media "evidence" (capture, authenticate, verify — courts increasingly admit it, and increasingly test it).