If one index covers only a couple of hundred sources, a complete search of available material is not possible using that one index. Although periodical indexes are usually thought of as means for finding the most recent literature available on a topic, periodical indexes can also help researchers identify valuable source of historical information. If, for example, a researcher needed to know what contemporary thought was on abortion in the 1920's, one way to discover this is to consult periodicals published during that time period. Some periodical indexes do provide indexing going back even into the 19th century. To find contemporary thought during a historical time period, a researcher will need to explore periodicals published during that period.
Periodical indexes provide the wherewithal to do so.
Some periodical indexes also provide selective indexing to newspaper articles in major newspapers. The extent to which they cover a newspaper's content varies, but is usually limited to articles of national or international interest. To provide complete access to news items included in their pages, major newspapers like the New York Times , the Times of London , and the Washington Post have their own indexes. A thorough search of a newspaper can be accomplished ONLY by using a newspaper index. For coverage of many newspapers, regional, national, and international in scope, a researcher might wish to investigate using NewsBank or the Lexis-Nexis collection of newspapers.