References
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2. GP “TsDU TEK”. Osnovnye pokazateli raboty neftyanoy i gazovoy otrasley
toplivno-energeticheskogo kompleksa Rossii za yanvar'-mart 2012 g. (Key
performance indicators of the oil and gas industries of Russia in January-
March 2012 according to CDD FEC), Neftyanoe khozyaystvo – Oil Industry,
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3. Stata longitudinal data reference manual: Release 11.0, Texas: Stata Corporation,
College Station, Texas, 2009.