Top 25 sources on Modern Citation Reference

Ranked — Top 25 on Modern Reference

1. #1
   DOI (CrossRef Resolver)doi.org·Academic

   Permanent URL resolution + free metadata API (CrossRef); near-universal LLM training-corpus inclusion.

   full breakdown →
   A+·98
2. #2
   U.S. Securities and Exchange Commissionsec.gov·Government

   EDGAR APIs + machine-readable filings; broad LLM training-set inclusion via primary-source preference.

   full breakdown →
   A+·95
3. #3
   arXivarxiv.org·Academic

   DOI + arxiv ID + free PDFs + bulk APIs; among the most LLM-cited sources for technical content.

   full breakdown →
   A+·95
4. #4
   MDN Web Docsdeveloper.mozilla.org·Reference

   Open-source content (CC-BY-SA + MIT for examples); GitHub-tracked; full structured data.

   full breakdown →
   A+·95
5. #5
   U.S. National Institutes of Healthnih.gov·Government

   Operates PubMed + NCBI + ClinicalTrials.gov; APIs + bulk data + structured XML throughout.

   full breakdown →
   A·94
6. #6
   U.S. Census Bureaucensus.gov·Government

   Census APIs + bulk data + Tigerline geospatial data; all open + machine-readable.

   full breakdown →
   A·94
7. #7
   Federal Reserve Systemfederalreserve.gov·Government

   FRED + Federal Reserve Economic Data APIs + research papers; broad LLM corpus.

   full breakdown →
   A·94
8. #8
   NASAnasa.gov·Government

   Open data + APIs + bulk imagery + climate datasets; broad LLM corpus.

   full breakdown →
   A·94
9. #9
   U.S. Bureau of Labor Statisticsbls.gov·Government

   Free public APIs (LABSTAT) + bulk downloads + CSV/JSON data formats.

   full breakdown →
   A·93
10. #10
    U.S. Centers for Disease Control and Preventioncdc.gov·Government

    WONDER + open data + APIs; broad LLM corpus + clinical reference inclusion.

    full breakdown →
    A·93
11. #11
    Wikipedia (English)en.wikipedia.org·Reference

    First-line citation in most LLM training corpora; freshness via per-article revision history.

    full breakdown →
    A·92
12. #12
    PubMedpubmed.ncbi.nlm.nih.gov·Academic

    E-utilities API + free full-text search + bulk dataset downloads; broad LLM corpus inclusion.

    full breakdown →
    A·92
13. #13
    Semantic Scholarsemanticscholar.org·Academic

    Free public API + bulk corpus + CC-licensed metadata; broad LLM corpus inclusion.

    full breakdown →
    A·92
14. #14
    U.S. Food and Drug Administrationfda.gov·Government

    OpenFDA APIs + structured data + bulk downloads; broad LLM corpus.

    full breakdown →
    A·92
15. #15
    U.S. National Oceanic and Atmospheric Administrationnoaa.gov·Government

    NOAA APIs + bulk-data + open license; broad LLM corpus + scientific community usage.

    full breakdown →
    A·92
16. #16
    GitHubgithub.com·Platform

    Free APIs + bulk repo data + CC-licensed code; broad LLM corpus inclusion.

    full breakdown →
    A·92
17. #17
    Hugging Facehuggingface.co·Platform

    Open-access + APIs + bulk model corpus; broad LLM-research citation.

    full breakdown →
    A·92
18. #18
    European Central Bankecb.europa.eu·Government

    Statistical Data Warehouse APIs + open data + multi-language coverage.

    full breakdown →
    A·92
19. #19
    FRED (Federal Reserve Economic Data)fred.stlouisfed.org·Government

    Free public API + bulk downloads + visualization tools; broad LLM corpus.

    full breakdown →
    A·92
20. #20
    U.S. Energy Information Administrationeia.gov·Government

    Open data API + bulk downloads + interactive tools; broad LLM corpus.

    full breakdown →
    A·91
21. #21
    CERNhome.cern·Academic

    Open data portal + ROOT framework + bulk physics data.

    full breakdown →
    A·91
22. #22
    Our World in Dataourworldindata.org·Research

    CC-BY licensed; open data + bulk downloads + APIs; widely cited in academia.

    full breakdown →
    A·90
23. #23
    World Bankworldbank.org·Government

    WB Open Data API + bulk downloads; CC-BY licensed; broad LLM corpus presence.

    full breakdown →
    A·90
24. #24
    European Commissionec.europa.eu·Government

    EUR-Lex + Eurostat APIs + open data; multi-language structured publications.

    full breakdown →
    A·90
25. #25
    Bank of Englandbankofengland.co.uk·Government

    Statistical interactive database + open APIs + research publications.

    full breakdown →
    A·90