BIBLIOGRAPHIA IRANICA: Yezidism and Yezidi Studies. Notice of a thematic journal issue: Kreyenbroek, Philip G. & Khanna Omarkhali (eds.). 2016. Yezidism and Yezidi Studies in the early 21st century (Special Issue. Vol. 4, No 2, Kurdish Studies). London: Transnational Press. Some of the material in the issue is available online for free.
Cross-file under Yazidi Watch. Background on the Yazidis, their Gnosticism-themed religion, and their tragic fate in the hands of ISIS, is here with many links.