1. “The Technology of Low-Temperature Carbonization”;Gentry,1928
2. Utah Conservation and Research Foundation; “Low-Temperature Carbonization of Utah Coals.” Quality Press, Salt Lake City, Utah, 1939.
3. E. O. Rhodes, U. S. Bureau Mines Inform. Circ. No. 7490 (1949); G. L. Kennedy, J. Inst. Fuel 33, 598(1960).