Background information for understanding the current crisis in Yemen

I’m not, and don’t pretend to be, an expert on the politics of Yemen.  But, for any who would like some background information on the Zaydi Shi‘ite movement out of which the Houthi insurgents emerge who have just taken control of that country — the Zaydis are quite distinct from the Ithna‘asharis who rule Iran — there may be worse places to look than my online article on the “Zaydiyya” for Oxford Bibliographies:

http://www.oxfordbibliographies.com/view/document/obo-9780195390155/obo-9780195390155-0153.xml