| Ranking | Source | Link |
| 1 | APA PsycInfo | https://www.apa.org/pubs/databases/psycinfo |
| 1 | ERIC (Education Resources Information Center) | https://eric.ed.gov/ |
| 1 | Library of Congress Subject Headings | https://id.loc.gov/authorities/subjects.html |
| 1 | Medical Subject Headings, NIH, National Library of Science | https://www.nlm.nih.gov/mesh/meshhome.html |
| 1 | Science.gov | https://www.science.gov/scigov/desktop/en/results.html |
| 2 | AGRIS – International System for Agricultural Science and Technology | https://www.fao.org/themes/en |
| 2 | Art & Architecture Thesaurus, The Getty Research Institute | https://www.getty.edu/research/tools/vocabularies/aat/ |
| 2 | BARTOC.org (Basel Register of Thesauri, Ontologies & Classifications) | https://bartoc.org/ |
| 2 | BioPortal | https://bioportal.bioontology.org/ |
| 2 | BIOSIS Previews | https://images.webofknowledge.com/WOKRS522_2R1/help/BIOSIS/index.html |
| 2 | Digital Europa Thesaurus | https://vocabularyserver.com/det/en/ |
| 2 | Embase Emtree | https://www.embase.com/emtree |
| 2 | EU Vocabularies, European Union | https://op.europa.eu/en/web/eu-vocabularies/ |
| 2 | Geopolitical entities, names, and codes, Director of National Intelligence | https://www.dni.gov/index.php/who-we-are/organizations/ic-cio/ic-cio-related-menus/ic-cio-related-links/ic-technical-specifications |
| 2 | ICONCLASS | https://iconclass.org/ |
| 2 | IEEE Thesaurus, Institute of Electrical and Electronics Engineers | https://www.ieee.org/publications/services/thesaurus.html |
| 2 | Legislative Indexing Vocabulary, US Department of Justice Programs | https://www.ojp.gov/ncjrs/virtual-library/abstracts/legislative-indexing-vocabulary-crs-thesaurus-20th-edition |
| 2 | Newspaper Genre List, University Libraries, University of Washington | https://www.lib.washington.edu/gmm/collections/mcnews/ngl |
| 2 | Nomenclature for Museum Cataloging | https://page.nomenclature.info/apropos-about.app?lang=en |
| 2 | OCLC (Online Computer Library Center) | https://www.oclc.org/en/home.html |
| 2 | Ontobee | https://ontobee.org/ |
| 2 | Research Vocabularies Australia | https://vocabs.ardc.edu.au/ |
| 2 | Thesaurus for Graphic Materials | https://www.loc.gov/rr/print/tgm1/ |
| 2 | Universal Decimal Classification | https://udcsummary.info/php/index.php |
ICGN131 DSearch 