The Internet Encyclopedia of Philosophy (IEP) (ISSN 2161-0002) was founded in 1995 to provide open access to detailed, scholarly, peer-reviewed information on key topics and philosophers in all areas of philosophy.

18 OA reference titles (as of Nov. 2021). In total, Brill today publishes more than 360 journals and 2,000 new books and reference works each year as well as a large number of databases and primary source research collections.

Founded by the late Professor Ehsan Yarshater and edited at the Ehsan Yarshater Center for Iranian Studies at Columbia University, this monumental international project brings together the scholarship about Iran of thousands of authors around the world.

iranicaonline.org The Encyclopaedia Iranica is a comprehensive research tool dedicated to the study of Iranian civilization in the Middle East, the Caucasus, Central Asia, and the Indian subcontinent...

Oxford University Press publishes many valuable reference resources. The overwhelming majority of the content is behind a paywall (libraries usually subscribe), however this list of OA entries from various OUP titles might prove to be useful in and of itself, but it could also lead researchers to a dictionary or encyclopedia that will fill an information gap.