1. Trace Element Geochemistry of Coal Resource Development Related to Environmental Quality and Health, PECH Report,1980
2. L.B. Clarke, L.L. Sloss, Trace Elements Emissions from Coal Combustion and Gasification, IEACR/49, IEA Coal Research, London, July 1992.
3. R.M. Davidson, Modes of Occurrence of Trace Elements in Coal, (2000), IEA Coal Research, The Clean Coal Center, CCC/36, London, England.
4. Coal cleaning controls HAP emissions;Akers;Power Eng.,1996
5. Role of coal cleaning in control of air toxics;Akers;Fuel Process. Technol.,1994