A History of Rome to 565 A. D.
CHAPTER XVIII
Von Domazewski, _Römische Kaiser_, ii, pp. 168–318; Gibbon, E., _Decline and Fall of the Roman Empire_, ed. Bury, i, chs. i–xii; Niese, _Geschichte_, pp. 331–376; Schiller, _Römische Kaiserzeit_, vol. i, ch. ii, §§ 57–59; chs. iii–iv; Stuart Jones, chs. v–ix. More special: Gregorovius, F., _The Emperor Hadrian_; Platnauer, M., _The Life and Reign of Septimius Severus_; J. Stuart Hay, _The Amazing Emperor Heliogabalus_.