References
- Bondev , I. 1991 . “ The vegetation of Bulgaria ” . In Map 1:600 000 with explanatory text , Sofia : St Kliment Ohridski University Press (in Bulgarian .
- Bronk Ramsey , C. 2005 . OxCal Program Ver. 3.10 , Oxford : University of Oxford Radiocarbon Accelerator Unit .
- Ivanov , K. 1964 . The lakes in Bulgaria , Sofia : Nauka i Izkustvo (in Bulgarian .