Roman cities in Bulgaria : [Colonia Ulpia Oescensium, Durostorum, Nicopolis ad Istrum, Abritus, Serdica, Pautalia, Nicopolis ad Nestum, Philippopolis, Diocletianopolis, Augusta Traiana, [...] / ed. by Rumen Ivanov. Sofia : Prof. Marin Drinov Acad. Publ. House, 2012