Al-Mo'tasim and al-Wathik
(Last visit: 28/1/2008)
The chapter about Al-Motasim in the book by W. Muir, The The Caliphate. Its rise, decline and fall, from original sources (ed. revised by T.H. Weir, Edinburgh 1924).
Ninth-century Byzantine Army
(Last visit: 5/7/2007)
Article by W.T.Treadgold «Notes on the numbers and organisation of the ninth-century Byzantine army» στο Greek, Roman and Byzantine Studies 21 (1980), pp. 269-88, from the web site www.deremilitari.org
(Last visit: 20/6/2007)
Prosopographic entry about emperor Theophilos in Wikipedia.