1. R. R. Ruch, H. J. Gluskotev, and N. F. Shimp, “Occurrence and Distribution of Potentially Volatile Trace Elements in Coal”, Environmental Geology Notes, Report Number EGN-72, Aug. 1974.
2. The coke samples were provided by the Monsanto Industrial Chemicals Company, Columbia, Tennessee.
3. The fly ash samples were provided by the Canadian Center for Mineral and Energy Technology, Ottawa, Canada.
4. National Bureau of Standards standard reference material 1632 and 1633.
5. Spex Industries Incorporated, P. 0. Box 798, Metuchen, New Jersey 08840.