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2. V. Zlatarski, History of Bulgarian state during the Middle Ages (Academic Press Marin Drinov, Sofia, 1994), (in Bulgarian) Vol. 1, Part 2
3. D. Aladzhov, Bulletin of the Museums from South-East Bulgaria 20, 17 (1994) (in Bulgarian)
4. I. Petrov, M. Slavova, Historical monument “Mezek” (Historical museum Press, Haskovo, 2002), (in Bulgarian)
5. R. Djingova, I. Kuleff, Arhaeometry 34, 53 (1992)