1. Nagraj, D. R., L. McAllister, P. Somasundaran, Int. J. Mineral Processing4, 111 (1977).
2. Gary, J. J., I. L. Field, E. G. Davis, U.S. Bureau of Mines, Rep. Invest. 6163 (1963).
3. Lamont, J. T. McLendon, L. W. Clements, Jr.,I. L. Field, U.S. Bureau of Mines, Rep. Invest. 8089 (1975).
4. Boyle, J. R., U.S. Bureau of Mines, Inform. Circ. 8404 (1969).
5. Boyle, J. R., U.S. Bureau of Mines, Inform. Circ. 8668 (1975).