1. Determination of mixing times of a paddle mixer with rapid discharge for production of dry mortar and plaster;Sommer;Aufbereitungstechnik/Mineral Processing,1989
2. Compare the mixing quality between a continuous solid mixer and discontinuous solid mixer (only German language available);Raasch;Schüttgut,1995
3. K. Sommer, Sampling of Powders and Bulk Materials, Springer Verlag Berlin Heidelberg New York, Tokyo 1986 ISBN 0-387-15891-X (U.S.).
4. Principles and systematics of the counting procedure for particle size analysis (only German language available);Alex;Aufbereitungstechnik/Mineral Processing,1972
5. Sphericity and roundness of rock particles;Wadell;The Journal of Geology,1933