<P> In a subject catalog, one has to decide on which classification system to use . The cataloguer will select appropriate subject headings for the bibliographic item and a unique classification number (sometimes known as a "call number") which is used not only for identification but also for the purposes of shelving, placing items with similar subjects near one another, which aids in browsing by library users, who are thus often able to take advantage of serendipity in their search process . </P> <P> Online cataloging, through such systems as the Dynix software developed in 1983 and used widely through the late 1990s, has greatly enhanced the usability of catalogs, thanks to the rise of MARC standards (an acronym for MAchine Readable Cataloging) in the 1960s . </P> <P> Rules governing the creation of MARC catalog records include not only formal cataloging rules such as Anglo - American Cataloguing Rules, second edition (AACR2), Resource Description and Access (RDA) but also rules specific to MARC, available from both the U.S. Library of Congress and the OCLC, the Online Computer Library Center global cooperative which builds and maintains WorldCat . </P> <P> MARC was originally used to automate the creation of physical catalog cards, but its use evolved into direct access to the MARC computer files during the search process . </P>

A catalog is not useful for finding which of the following things