Reference sources of a category
Also called: Citation Core, most-cited sources
Definition
In every industry, a small group of sites comes back in most AI answers. The Semrush AI Visibility Index 2026 calls them the “Citation Core”: G2 and Capterra for software, TripAdvisor for travel, NerdWallet or Investopedia for finance in the United States. In France, the equivalents vary by industry.
These sources shape what AI says about a whole category. A brand that's missing from these sites, or poorly presented there, starts at a disadvantage, even if its own site is excellent. That's often where GEO plays out, more than on the brand's site.
Example
For B2B software, being well rated on G2 and Capterra, with recent reviews, weighs more in ChatGPT's answers than three blog posts published on its own site.
What it means for your AI visibility
Find out which sources AI cites on your questions, then work on your presence there: up-to-date listings, recent reviews, a place in the comparisons. The page that counts isn't always yours.
In i am rankCitation analyticsSee which sources AI cites on your questions, and which ones talk about you.Related terms
- CitationA citation is when an AI points to a page as a source of its answer, with a link. Unlike a plain mention, it can bring traffic.
- Digital PRDigital PR gets a brand talked about in media and on third-party sites. In GEO, it's often what gets a brand into AI answers.
- UGCUGC covers content published by users: reviews, forums, Reddit, videos. AI relies on it heavily to size up a brand.
- E-E-A-TE-E-A-T stands for the four qualities Google looks for in content: experience, expertise, authoritativeness and trustworthiness.
- Brand mentionA mention is when an AI names your brand in its answer, with or without a link to your site.
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