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Nikolova, Kapka Sofia互联网档案馆的存檔,存档日期20 August 2020. University of Indiana. "Emperor Constantine the Great even considered the possibility for Serdika to become the capital of the Eastern Roman Empire"
Slaviani. 1967 [27 June 2019]. (原始内容存档于18 August 2020).
Godisnjak. Drustvo Istoricara Bosne i Hercegovine, Sarajevo. 1950: 174 [27 June 2019]. (原始内容存档于18 August 2020). Санџак Софија Овај је санџак основан око г. 1393.