The Institute for Scientific Information (ISI) manages an indexing system of scientific journals. It features three main lists of journals: the Science Citation Index, the Social Science Citation Index and the Arts and Humanities Citation Index.
As of 2015, the database includes more than 17,000 journals. The full list of indexed journals is accessible at ThomsonReuters.com. Inclusion in this list requires journals to fulfill certain selection criteria, so being included is an indicator of the quality of the journal. Criteria for selection include basic publication standards, the editorial content of the journal, the international diversity of the contributing authors and the citation data of the articles in the journal.
ISI started its indexing system in 1964. In 1992, Thomson Reuters bought ISI and continued to manage the journals database.