Best sources for AI engines (ChatGPT, Claude, Perplexity) by Modern Citation Reference

Same 15 sources, re-sorted by Modern Citation Reference only — different signal than the composite Index. The leader changes: DOI (CrossRef Resolver) takes the top position at A+ · 98.

1. 1
   DOI (CrossRef Resolver)doi.org↑3

   International standard identifier resolver for academic citations (~150M+ DOIs).

   Modern Reference A+ · 98·Index A+ · 95·Academic
   A+·98
2. 2
   U.S. Securities and Exchange Commissionsec.gov↑1

   Primary-source regulator publishing every public-company filing (13F, 10-K, 8-K, etc.) since 1934.

   Modern Reference A+ · 95·Index A+ · 96·Government
   A+·95
3. 3
   arXivarxiv.org↑7

   Open-access preprint server for physics, mathematics, computer science; ~2.4M papers since 1991.

   Modern Reference A+ · 95·Index A · 89·Academic
   A+·95
4. 4
   U.S. National Institutes of Healthnih.gov↓3

   U.S. federal medical research agency operating PubMed, NCBI, MedlinePlus, and trial registries.

   Modern Reference A · 94·Index A+ · 95·Government
   A·94
5. 5
   Federal Reserve Systemfederalreserve.gov

   U.S. central bank; primary source for monetary policy + economic data + financial-system statistics.

   Modern Reference A · 94·Index A+ · 95·Government
   A·94
6. 6
   U.S. Census Bureaucensus.gov↑5

   Federal statistical agency for U.S. demographic + economic data; primary-source decennial census + ACS surveys.

   Modern Reference A · 94·Index A · 94·Government
   A·94
7. 7
   U.S. Bureau of Labor Statisticsbls.gov

   Federal statistical agency for U.S. labor + price data; CPI, employment, unemployment, productivity.

   Modern Reference A · 93·Index A · 94·Government
   A·93
8. 8
   U.S. Centers for Disease Control and Preventioncdc.gov↑1

   Federal agency for U.S. public-health surveillance + disease prevention; primary-source MMWR + WONDER data.

   Modern Reference A · 93·Index A · 94·Government
   A·93
9. 9
   Wikipedia (English)en.wikipedia.org↓7

   Crowd-edited encyclopedia with ~7M articles and per-article inline citation discipline.

   Modern Reference A · 92·Index A · 94·Reference
   A·92
10. 10
    PubMedpubmed.ncbi.nlm.nih.gov↓4

    U.S. National Library of Medicine literature index covering ~36M biomedical citations.

    Modern Reference A · 92·Index A · 94·Academic
    A·92
11. 11
    U.S. Food and Drug Administrationfda.gov↓3

    Federal agency for food + drug + medical-device safety; primary-source approvals + safety alerts.

    Modern Reference A · 92·Index A · 94·Government
    A·92
12. 12
    European Central Bankecb.europa.eu↑3

    EU central bank; primary source for euro-area monetary policy + financial-system data.

    Modern Reference A · 92·Index A · 93·Government
    A·92
13. 13
    European Commissionec.europa.eu↑1

    EU executive branch publishing primary-source policy + statistics + legislation.

    Modern Reference A · 90·Index A · 92·Government
    A·90
14. 14
    The New York Timesnytimes.com↓2

    U.S. national newspaper of record, founded 1851. Pulitzer Prize record + investigative depth + structured-data-rich web platform.

    Modern Reference B · 82·Index A · 88·News
    B·82
15. 15
    Bloomberg Newsbloomberg.com↓2

    Business + finance newsroom feeding the Bloomberg Terminal; broad data infrastructure + global beat coverage.

    Modern Reference B · 75·Index B · 83·News
    B·75