1. BP. Statistical review of world energy. June 2001.
2. Coal Information 1995, 1996, 1998, 2000,1995-1996-1998-2000
3. Coal Week International (CWI) New York (USA). Platts—A Division of McGraw-Hill Company 1990–2001 [selected issues].
4. Commodity markets and the developing countries. A World Bank Quarterly, 1995–1998.
5. Global commodity markets. A comprehensive review and price forecast. A World Bank Quarterly, 1999–2000. 2001 data available from:: www.worldbank.org.