Factors Expediting the Rise of the Ottomans and the Fall of the Second Bulgarian Empire
- Creasy Edward S.; History of the Ottoman Turks – from the beginning of their Empire to the Present Time; Richard Bentley and Son, London, 1877, p 1 – 51
- Kinross Lord: The Ottoman Centuries – The Rise and Fall of the Turkish Empire, Jonathan Cape, London, 1977, p 15 – 43
- Sugar Peter; A History of East Central Europe, Volume V – South-Eastern Europe under Ottoman Rule, 1354 – 1804, University of Washington Press, Seattle and London, 1977, p 3 -31
- Gibbons Herbert Adams: The Foundation of the Ottoman Empire – A History of the Osmanlis up to the Death of Beyazid I (1300 – 1403), Oxford, The Clarendon Press, 1916, p 54 – 231
- Mazower Mark: The Balkans, from the End of Byzantium to the present day; Phoenix, London, 2000 p 6 – 18 – 49 -77
- Панайотов Панайот: История на България; Българско Средновековие – Извори, Факти, Мнения, Абагар, Велико Търново, 1998, ст 493- 538
- Goffman Daniel: The Ottoman Empire and the Early Modern Europe, Cambridge University Press, Cambridge, p 29 – 41
- Byzantium – an Introduction to East Roman Civilization; edited by Norman H Baynes and H. St L. B. Moss, Clarendon Press, Oxford, 1949, The Byzantine Inheritance in South-eastern Europe by William Miller, p 326 – 337
- Byzantium – an Introduction to East Roman Civilization; edited by Norman H Baynes and H. St L. B. Moss, Clarendon Press, Oxford, 1949, Byzantium and the Slavs, Steven Runciman, p 338 – 368
- Crowley Roger: Constantinople – the Last Great Siege 1453, Faber and Faber, London, 2006, 23 – 36
- Orbini Mavro: Kraljevstvo Slavena; Prevela Snežana Husić; POVIJEST HRNATSKIH POLITIČKIH IDEJA; Golden marketing, Zagreb, Narodne Novine, Zagreb, 1999