ebrary, Inc, Leonard, J. W., & Hardinge, B. C. (1991). Coal preparation (5th ed.). Society for Mining, Metallurgy, and Exploration.

ebrary, Inc, Joseph W. Leonard, and Byron C. Hardinge. Coal Preparation. 5th ed. Littleton, Colo.: Society for Mining, Metallurgy, and Exploration, 1991.

ebrary, Inc, et al. Coal Preparation. 5th ed. Society for Mining, Metallurgy, and Exploration, 1991.