1. J.R. Rhodes, J.C. Daglish and C.G. Clayton, “A Coal Ash Monitor with Low Dependence on Ash Composition,” Radioisotope Instruments in Industry and Geophysics, 1966, I, 457.
2. I.S. Boyce, C.G. Clayton and D. Page, “Some Considerations Relating to the Accuracy of Measuring the Ash Content of Coal by X-ray Backscattering,” Nucl. Tech. Miner. Resour., Proc. Int. Symp. 1977, IAEA: Vienna, Austria, 135–65 (1978).
3. F.V. Brown and S.A. Jones, “On Site Determination of Ash in Coal Utilizing a Portable XRF Analyzer,” Advances in X-ray Analysis 23, 57 (1980), Plenum Publishing Corp., New York.
4. Jacques Renault, “Rapid Determination of Ash in Coal by Compton Scattering, Ca and Fe Fluorescence,” Advances in X-ray Analysis 23, 45 (1980), Plenum Publishing Corp., New York.
5. American Society for Testing & Materials, 1977 Annual Book of Standards, pt. 26, 370 (1977).