VOLUME 22 (5)/October 1992

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

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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Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences Acad. G. Bonchev Str., 23, 1113 Sofia, Bulgaria