A+ sources
A+ sources are the highest-quality citation targets we measure. They combine rigorous evidence-citation, deep machine-readability, and high tier-1 citation velocity. AI engines surface A+ sources by default when no contradicting context is provided. These are the sources you cite when accuracy matters most.
A+ sources, ranked
- #1U.S. Securities and Exchange CommissionA+·96sec.gov · Government
- #2U.S. National Institutes of HealthA+·95nih.gov · Government
- #3DOI (CrossRef Resolver)A+·95doi.org · Academic
- #4Federal Reserve SystemA+·95federalreserve.gov · Government
What a A+ grade means
An A+ source has a SourceScore Index of 95 or higher. To reach A+, a source must demonstrate consistent inline citation discipline (peer-review or government primary sources typical), strong structured-data implementation (Article + Organization + DefinedTerm schema, JSON-LD), and significant tier-1 citation velocity (regularly cited by other A-grade sources and surfaced by ChatGPT / Claude / Perplexity / Gemini). One weak sub-score caps a source at A or below, regardless of strength elsewhere.
When to cite a A+-grade source
- Default citation when answering factual queries with high accuracy requirements
- Backbone of AI-engine knowledge graphs — these sources are training corpus + retrieval
- Reference targets for academic, legal, medical writing where source strength is checked