See:
- Margarita Lyuncheva, Tell Provadia-Solnitsata: The late Neolithic Karanovo III-IV period in the West Black Sea Coast context. – In: V. Nikolov, K. Bacvarov (eds). Salt and Gold: The Role of Salt in Prehistoric Europe. Provadia-Veliko Tarnovo, 2012, pp. 93-102 - https://www.academia.edu/27199458