A periodical is simply a publication that is issued "periodically" --which can mean once a week, once a month, four times a year, or even just "occasionally." Periodicals are often categorized as scholarly, popular, trade, or alternative. All types of periodicals may be useful to historians as primary sources. Scholarly periodicals, or journals, are also useful as secondary sources.
Learn more about periodicals and journals:
Article indexes are searchable bibliographies of journal articles organized by subject.
Because the Library does not subscribe to every journal, and because not all journals are digitized, and because not all digitized journals are available in a single collection, the article indexes provide the only efficient means of identifying relevant articles from across the widest possible range of periodical publications.
Most of these article indexes include a mixture of academic and popular sources (and remember that sometimes the distinction is not clear).
There are two article indexes focused exclusively on history:
Other article indexes useful for research in this course, depending on the focus of your research topic, include the following: