Fine, John Van Antwerp Jr. (1994). The Late Medieval Balkans: A Critical Survey from the Late Twelfth Century to the Ottoman Conquest. The University of Michigan Press.
Soli (province) Wikipedia
Soli or Só was the medieval name of a small region in today's northern Bosnia and Herzegovina, centered in the town of Tuzla. Initially, a Slavic župa, the Banate of Só became an administrative division of the Kingdom of Hungary. The meaning of the name is "salts". With the arrival of the Ottoman Empire around 1512, the names of the villages "Gornje Soli" and "Donje Soli" were translated to "Memlehai-bala" and "Memlehai-zir", literally meaning Upper and Lower Saltworks, resp.