APA (7th ed.) Zitazioa
Birley, A. (1999). Septimius Severus: The African emperor. Routledge.
Chicago Style (17th ed.) Zitazioa
Birley, Anthony. Septimius Severus: The African Emperor. London ; New York: Routledge, 1999.
MLA (9th ed.) Zitazioa
Birley, Anthony. Septimius Severus: The African Emperor. Routledge, 1999.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.