1. D. J. Brown ,Froth Flotation, D. W. Fuerstenau ed. , AIME , New York , p. 518 ( 1960 ).
2. F. F. Apian ,Flotation, A. M. Gaudin Memorial Volume, (M. C. Fuerstenau, ed. ), AIME , New York , p. 1235 ( 1976 ).
3. Hydroxyl contents of coals: new data and statistical analyses