Online Resources for the study of the Caliphate
List of Caliphs and Sultans
https://www.metmuseum.org/toah/hd/isru/hd_isru.htm
Islamic History Open Data Platform (Ghent University)
https://ihodp.ugent.be
Up-to-date guides to libraries and archives across North Africa, the Middle East, the Caucasus, and South Asia
https://www.arsheef.org/