A. PERSI (short for Periodical Source Index) is a database of references to articles in history and genealogy magazines and journals published in the United States and Canada as far back as 1800. (A searchable catalog of periodical titles is here.)
You can search PERSI for, say, a surname, town or topic, and results will show citations for articles related to your search term.
Examples of resources you might find using PERSI include a historical society journal article that mentions your ancestor, an out-of-print magazine about a family hometown, or a how-to magazine with hints for doing research in the old country.
Note PERSI doesnt have the articles themselvesrather, it has the title, date and other information that will help you find the article of interest.
The PERSI database is searchable through HeritageQuest Online, a genealogy data service available free through many public libraries (check your librarys Web site or ask at the reference desk) or at Allen County, Ind., public library location. (The Allen County librarys genealogy staff compiled and updates PERSI.)
Subscription Web site Ancestry.com also has PERSI, though its version isnt as up-to-date as the others mentioned.
Once you find a citation for an article you want, see if the publication is available through your library or another library near you. If not, ask if the library can borrow it (or at least get photocopies) through interlibrary loan. Another option: The Allen County Public Library has the periodicals that are indexed in PERSI; you can order photocopies for a fee using the form linked on this page.