1. Flint raw materials and artefacts from NE Bulgaria: a combined petrographic and LA-ICP-MS study;Andreeva;J. Lithic Studies,2014
2. Characterization of ‘Balkan flint’ artefacts from Bulgaria and the Iron Gates using LA-ICP-MS and EPMA;Bonsall;Interdiscip. Stud.,2010
3. Geological Map of Republic of Bulgaria in Scale 1:100 000, Shumen Map Sheet; Explanatory Note for the Geological Map of the Republic of Bulgaria in Scale 1:100 000, Shumen Map Sheet (in Bulgarian);Cheshitev,1995
4. Archaeological excavations of the multilayer settlement near the town of Varbitsa, Shumen region (in Bulgarian with English summary);Grigorov,2016
5. Appendix 6: SILLS: a Matlab-based program for the reduction of laser ablation ICP-MS data of homogeneous materials and inclusions;Guillong,2008