1. C.J. McKenny et al., Coal flotation process, US Patent, 5,443,158 (1995).
2. W.-W. Wen et al., Method for simultaneous use of a single additive for coal flotation, dewatering, and reconstitution, US Patent, 5,379,902 (1995).
3. D.J.A. McCaffrey et al., Froth flotation, US Patent, 4,528,107 (1985).
4. The determination of phosphorus in coal ash;Cosstick;Fuel,1959
5. High-temperature chlorination of coal ash in a fluidized bed: 1. Recovery of aluminum;Mehrotra;Ind. Eng. Process Des. Dev.,1982