Sources:
- Pernicheva-Perets, Liliana, Malgorzata Grebska-Kulow, and Ilija Kulov,, Balgarchevo: The Prehistoric Settlement, Volume I, Craft House Bulgaria, 2011
- A. Bakamskam Miroslav Abrashev, Ruslan Kostov, (2018). Omphacite-bearing axes from the Early Neolithic site Galabnik (Western Bulgaria): mineral identification by Raman spectroscopy.. Review of the Bulgarian Geological Society. 79. p. 51-57.