As a result of the proliferation of the primary
literature and the quantity and diversity of secondary publications, a secondary indexing is required to
facilitate access to primary and secondary sources.
The tertiary sources which provide this indexing include guides to the literature and library catalogs.
|Guides to the Literature||Guides to the literature describe the types of sources, in all formats, available for one or more disciplines, and list outstanding examples of each type. Some guides cover all aspects of science and technology, while others focus on a specific discipline.
|Library Catalogs||Library catalogs index all items in any format held in a particular library. Books, journals, newspaper, government publications, reference materials, and non-textual materials such as films, videos, computer software, maps, photographs are some of the items that may be included. In addition, library catalogs are now beginning to include records for items that are not physically held in the library, but which can be accessed by authorized users, such as electronic journals or databases.
A catalog record includes both a bibliographic and physical description of the item, subject indexing, the physical location and call number of the item within the library.
Individual library catalogs from all over the world can now be accessed via the Internet.
WorldCat is the union catalog of all items cataloged by OCLC member libraries. It includes over 43 million records for books, computer data files, computer programs, films, journals, manuscripts, musical scores, newspapers, slides, sound recordings, and videos. WorldCat does NOT index journal or newspaper articles or book chapters.