- AgNIC - Agriculture Network Information Center provides a searchable database for agricultural information available on the Internet.
- AGRICOLA - Bibliographic database of agricultural literature from the National Agricultural Library.
- The British Library - Search the British Library Public Catalogue, the Document Supply Catalogue, or specialized collections.
- Center for Research Libraries - Search the CRLCATALOG, or specialized catalogs for foreign dissertations, foreign newspapers, and ethnic press (periodicals and newspapers published by ethnic groups in North America).
- Chronicling America - "This site [from the Library of Congress] allows you to search and view newspaper pages from 1880-1922 and find information about American newspapers published between 1690-present." The directory on this site is particularly useful, as it lists library holdings including format and specific dates held.
- CiNII: Scholarly and Academic Information Navigator - Produced by the National Institute of Informatics, Japan. This is a database service that enables searching of information on academic articles published in academic society journals or university research bulletins, or articles included in the National Diet Library's Japanese Periodicals Index Database.
- CISTI Online Catalogue - Search the Canada Institute for Scientific and Technical Information catalog by author, title, subject, keyword, or standard number.
- ERIC - Educational Resources Information Center. Includes ERIC search and thesaurus. Some items available full-text through this site.
- Gateways to union catalogs - National libraries and archives internal page.
- GBV - Common Library Network of the German States
- LibWeb - Library pages from over 135 countries
- National Technical Information Service catalog - Contains 450,000 government publications issued by NTIS since 1990. Also contains links to searchable databases for specialized NTIS collections such as Business, Environmental, or Military Publications and Manuals.
- Index Theologicus citations to documents from over 600 theological journals, Festschriften , and congresses (Universität Tübingen)
- USGS Publications Warehouse the advanced search feature allows you to locate or verify USGS publications by report series, number, author, year, and can be helpful in locating a monograph title if you have only a series title and number.
- BOL.com - Dutch equivalent of Amazon
- DealTime - Click on "Books" tab. Gives book prices for multiple booksellers so you can comparison shop.
- ILL-L - When all else fails, post a message to the discussion list asking people for help with a citation. Put "help with citation" in the subject line, and be sure to indicate what sources you have already checked.
- LibDex - worldwide directory of library homepages and web-based OPACs.
- Project Wombat - for difficult to answer reference questions; formerly known as Stumpers-L.