VOLUME 49 (2)/August 2020

Department of Mineralogy and Petrography, University of Mining and Geology “St Ivan Rilski”, 1700 Sofia, Bulgaria
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University of Chemical Technology and Metallurgy, 8 Kl.Ohridsky Blvd, 1756 Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria