The coinage of Byzantium for Septimius Severus and his two sons up to 212 A.D. Notes on its chronology - Boteva, D. (Poseliščen život v drevna Trakija. III Meždunaroden sumposium "Kabile", Jambol 17 - 21 maj 1993. Dokladi. Studies on settlement life in ancient Thrace. Proceedings of the IIIrd International Symposium "Cabyle", Jambol 17 - 21 May 1993)