1. BP Energy Outlook 2035 (BP, 2016, available at: http://www.bp.com/energyoutlook; 12-04-2016)
2. Annual Reports, Facts and trends (Verein der Kohleimporteure, Hamburg, Editions of years 2006- 2015, available at: http://www.kohlenimporteure.de/home.html; 12-04- 2016)
3. Coal Information (IEA, Paris, Editions of years 2004-2015)
4. IDA JSC,Podstawowe informacje o rynku oraz sektorze węgla kamiennego(IDA JSC Branch Office in Katowice within the framework of the “Programme of statistical surveys” - a statistical survey “Mining of hard coal and lignite” conducted by the Ministry of Economy, Katowice, Editions of years 2012-2016)