1. Ash at Work XII(2);National Ash Association,1980
2. U.S. Overview of Ash Production and Utilization;Faber,1976
3. Evaluation of Potential Processes for Recovery of Metals from Coal Ash;Canon;EPRI CS 1992,1981
4. Chemistry of the Recovery of Alumina from Fly Ash;Kelmers,1981
5. Evaluation of Potential Processes for the Recovery of Resource Materials from Coal Residues;DeCarlo;ORNL/TM-6126,1978