Online Reference Sources

These are resources that professional indexers may find useful in their daily work.

Thesauri will be found by subject on this page. For additional resources, consult ASI's list of online thesauri.

And, as always, ASI does not endorse or promote products, companies, political parties, religious groups, advertising or information found in web sites we provide links for.

General Reference Sources Specific Reference Sources

General Reference Sources


  • Dictionaries, Thesauri, and Other Language Tools
      • German/English Translation Service. This isn't a Web page; the LEO translation services is a translation-by-email service. Put words you want to have translated into the email message body and receive a translation in reply. (Note that the service translated individual words, not sentences.) Send your email message to with no subject and the message body of your words-to-be-translated.
      • Language Dictionaries. List of language dictionaries.
      • Library of Congress Controlled Vocabularies. Includes link to CRS Legislative Subject Terms (formerly Legislative Indexing Vocabulary (LIV)).
      • Library of Congress Thesaurus for Graphic Material I and II. (NOTE there are two distinct and separate links: one for volume I and one for volume II.) If you are looking for a thesaurus of terms related to graphic materials, this is where you want to be exploring. For browsing and searching.
      • LookWayUp Dictionary. This dictionary and thesaurus site allows approximate spellings on look-up and combines a multilingual dictionary, thesaurus, translation, and other handy tools. The built-in thesaurus gives synonyms, antonyms, and up to 25 types of related terms.
      • Merriam-Webster Dictionary. Search only.
      • National Information Standards Organization (NISO) standards page includes access ANSI/NISO Z39.19 - 2005 Guidelines for the Construction, Format, and Management of Monolingual Controlled Vocabularies (Related international standard: ISO 2788). This standard presents guidelines and conventions for the contents, display, construction, testing, maintenance, and management of monolingual controlled vocabularies. It focuses on controlled vocabularies that are used for the representation of content objects in knowledge organization systems including lists, synonym rings, taxonomies, and thesauri. Available for a fee.
      • Onelook dictionary. Search only. (For browsing, see You can choose to look up your word in one dictionary or through all of the variety of specialized and general dictionaries available. A great source! Contains listings for over 200 searchable dictionaries.
      • Online Dictionary of Language Terminology. The ODLT is an online dictionary of language terminology that consists of concise, simply worded explanations of terms that English speakers use to talk about the English language.
      • Online English Grammar.
      • The Wordsmyth English Dictionary-Thesaurus. Search only. Search for words, close matches, synonyms, and so on. Much more than a dictionary.
      • The World Bank Thesaurus. Search or browse by letter.
      • Transportation Research Thesaurus. The Transportation Research Thesaurus was developed to provide a tool to improve the indexing and retrieval of transportation information. The thesaurus covers all modes and aspects of transportation. A primary use will be to provide a common and consistent language between producers and users of the Transportation Research Information Services (TRIS) Database. The thesaurus is currently also used as an indexing tool for federal, state and university collections. The TRT Web site allows users to access terminology through Alphabetical, Hierarchical, Keyword In Context or Keyword Out of Context displays. The full display shows relationship of terms including SN (Scope Notes), UF (used for terms), BT (Broader Term), NT (Narrower Term), and RT (Related Term).
      • Dictionaries of computer terms.
      • Science glossaries.
    • Encyclopedias, Collections of Information, and Fact Books
      • CIA World Factbook.
      • Encyclopædia Britannica. A classic and now completely free online.
      • Articles from Concise Columbia Electronic Encylopedia, Third Edition.
      • ERIC Thesaurus. ERIC (Educational Resources Information Center) is a national education database of bibliographic citations and digests, sponsored by the U.S. Department of Education. This online version of the ERIC Thesaurus provides immediate search access to portions of the ERIC database. The 40-member ERIC Vocabulary Review Group (VRG) presently oversees the Thesaurus development effort. Search only.
      • Flags of the World. An extensive site devoted to vexillology.
      • Geographic Names Information System (GNIS). Covers U.S.,  its territories, and Antarctica; the authoritative source of geographic names in the U.S.
      • Geographic Names Server (GNS). The official repository of standard spellings of all foreign geography names, sanctioned by the U.S. Board of Geographic Names (BGN).
      • Still can't find it? Try one of the following:
        • Encyberpedia (list of online encyclopedias).
        • Credo Reference (Formerly xrefer with access to over 50 dictionaries, fact books, and desktop encyclopedias not otherwise available online). SUBSCRIPTION basis only now but many libraries subscibe and you might be able to access it via your library membership!
    • Phone Directories, Organizational Listings, and Geographical Maps

      Art and Architecture Reference Sources


      • The Art & Architecture Thesaurus. The AAT is a controlled vocabulary for describing and retrieving information on fine art, architecture, decorative art, and material culture. This database is created and maintained by the Getty Information Institute, and endorsed by library, archives, and museum professional groups.
      • The Union List of Artist Names. The ULAN is a database of biographical and bibliographical information on artists and architects, including a wealth of variant names, pseudonyms, and language variants. This database is created and maintained by the Getty Information Institute, and endorsed by library, archives, and museum professional groups.

      Biographical Reference Sources