1. Statics and Kinematics of Granular Materials;Nedderman,1992
2. Sands, Powders, and Grains: An Introduction to the Physics of Granular Materials;Duran,2000
3. Minimum energy theorem for flow of dry granules through apertures;Brown;Nature,1961
4. The hour-glass theory of hopper flow;Davidson;Trans. Instn. Chem. Engrs.,1973