1. Organic titanium in coal and the deposition of titanium on direct liquefaction catalysts—an alternative view;Robbat;Fuel,1984
2. Non-fuel uses of coals and synthesis of chemicals and materials;Song;Fuel,1996
3. The preparation of ultra-clean coal in Germany;Crawford;Trans.—Inst. Min. Eng.,1951
4. L. Reggel, R. Raymond, B.D. Blaustein, Removal of mineral matter including pyrite from coal, United States Patent 3,993,455, 1976.
5. E.P. Stambaugh, Treating carbonaceous material, United States Patent 4,121,910, 1978.