VOLUME 24 (2)/April 1994

Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
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Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
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Geological Institute, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

Institute of Applied Mineralogy, Bulgarian Academy of Sciences, 6 Moskovska str., 1000 Sofia
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Institute of Ferrous Metallurgy, Botunec, 1770 Sofia