Periodicals Index Online index to millions of articles published in over 6,000 periodicals in the humanities and social sciences. It spans 37 key subject areas in the humanities and social sciences. Periodicals Index Online currently indexes over 20 million articles going as far back as 1665 in over 60 languages and dialects, including English, French, German, Italian, Spanish and other Western languages. Periodicals Index Online covers not only journals published by academic presses but also those journals published as popular reading.