1. Modes of occurrence of selected trace elements in several appalachian coals;Finkelman;Am. Chem. Soc. Div.,1979
2. D.J. Swaine, Trace Elements in Coal, Butterworth, London, 1990, pp. 278.
3. E.L. Obermiller, V.B. Conrad, J. Lengyel, Trace Element Contents of Commercial Coals, Proceedings, EPRI Conference on Managing Hazardous Air Pollutants: State-of-the-Art, November 4–6, 1991.
4. J. Kuhn, F. Fiene, R. Cahill, H. Gluskoter, N. Ship, Abundance of Trace and Minor Elements in Organic and Mineral Fractions of Coal, Illinois State Geological Survey, Environmental Geology Notes, No. 88, 1980.
5. C. Ford, A. Price, Evaluation of the Effect of Coal Cleaning on Fugitive Elements, Final Report, Phase III, BCR Report L-1304, 1982.