Turki bin Khalid bin Saad bin Abdulaziz Al Saud (2015). "Saudi Arabia-Iran relations 1929-2013"(PhD Thesis). King's College London. p. 40. Retrieved 29 January 2021.
loc.gov
catdir.loc.gov
Paul Dresch. (2000). A history of modern Yemen, Cambridge, pp. 28-88 [1].
"Yemen Ruler, Three Sons Die in Plot: Religious Leader Heads New Government as Nation's Unrest Ends". Hartford Courant. Associated Press. February 20, 1948. ProQuest561007035. (Subscription required.)
proquest.com
(The Saudis had become Imam Yahya's rival for the Emirate of Asir, and after a border war in 1934, Yahya was forced to concede Asir to Al Saud by the Treaty of Taif. A more fundamental cause of friction was the clash between the severely orthodox Wahhabism of the tribes that formed the basis of Al Saud power and the Zaidi sect of Shi'a practiced by the tribesmen who supported Yahya. See von Weisl, Wolfgang (May 1, 1927). "New Light on Arabia". The Living Age. Retrieved May 11, 2015. (Subscription required.)