Severus Alexander.com - Dedicated to the study of the Roman emperor (222-235) and his coinage. Essays, biography, bibliography, and images provided. - http://www.severusalexander.com/
De Imperatoribus Romanis: Alexander Severus - A scholarly biography by Herbert W. Benario of Emory University, illustrated with a portrait bust. - http://www.roman-emperors.org/alexsev.htm
Wikipedia: Alexander Severus - Article on this Roman Emperor, incorporating text from the 1911 Encyclopædia Britannica. - http://en.wikipedia.org/wiki/Alexander_Severus
Catholic Encyclopedia: Alexander Severus - An article by Thomas J. Shahan on the emperor who was born at Acco in Palestine in 208, and murdered by his mutinous soldiers at Sicula on the Rhine. - http://www.newadvent.org/cathen/13743a.htm