For the earlier part he used Widukind's Res gestae Saxonicae, the Annales Quedlinburgenses and other sources; the latter part is the result of personal knowledge.
See the contemporary life by Vitorelli, continuator of Ciaconius, Vitae et res gestae summorum pontiff.
On the walls of the temple is engraved the famous Monumentum Ancyranum, a long inscription in Latin and Greek describing the Res gestae divi Augusti; the Latin portion being inscribed on the inner left-hand wall of the pronaos, the Greek on the outside wall of the naos (cella).
Ancyr., Mommsen, Res gestae divi Augusti (1883); and Inscr.
See Guarnacci, Vitae et res gestae Pontiff.