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Voutov T. Bulgarian coal industry in market economy // Journal of Mining Institute. 2010. Vol. 185 . p. 196-198.
Mining production in Bulgaria during the transitional period goes through four periods: 1990 – beginning of the period; 1995 – restructuring of mining production, formation of normative base; 2000 – end of transitional period; 2005-2008 – sustainable development of mining industry.